Move readme to markdown

The recent changes to freshen up the readme don't render properly on
PyPI, because PyPI doesn't support

- The `raw` restructured text directive (but they do support raw html in
  markdown docs).
- The html `<picture>` tag in general

To work around this we move the readme to markdown, and drop the
light/dark rendering of the logo in the GitHub readme. We could support
this by transforming the readme before uploading to PyPI, but that seems
like too much work for too little benefit.

MANIFEST.in

@@ -5,6 +5,6 @@ include msgspec/*.pyi
 include msgspec/py.typed
 include setup.py
 include versioneer.py
-include README.rst
+include README.md
 include LICENSE
 include MANIFEST.in

README.md

@@ -0,0 +1,121 @@
+<p align="center">
+  <a href="https://jcristharif.com/msgspec/">
+    <img src="https://raw.githubusercontent.com/jcrist/msgspec/main/docs/source/_static/msgspec-logo-light.svg" width="35%" alt="msgspec" />
+  </a>
+</p>
+
+<p align="center">
+  <a href="https://github.com/jcrist/msgspec/actions/workflows/ci.yml">
+    <img src="https://github.com/jcrist/msgspec/actions/workflows/ci.yml/badge.svg">
+  </a>
+  <a href="https://jcristharif.com/msgspec/">
+    <img src="https://img.shields.io/badge/docs-latest-blue.svg">
+  </a>
+  <a href="https://github.com/jcrist/msgspec/blob/main/LICENSE">
+    <img src="https://img.shields.io/github/license/jcrist/msgspec.svg">
+  </a>
+  <a href="https://pypi.org/project/msgspec/">
+    <img src="https://img.shields.io/pypi/v/msgspec.svg">
+  </a>
+  <a href="https://anaconda.org/conda-forge/msgspec">
+    <img src="https://img.shields.io/conda/vn/conda-forge/msgspec.svg">
+  </a>
+  <a href="https://codecov.io/gh/jcrist/msgspec">
+    <img src="https://codecov.io/gh/jcrist/msgspec/branch/main/graph/badge.svg">
+  </a>
+</p>
+
+
+`msgspec` is a *fast* serialization and validation library, with builtin
+support for [JSON](https://json.org), [MessagePack](https://msgpack.org),
+[YAML](https://yaml.org), and [TOML](https://toml.io). It features:
+
+- 🚀 **High performance encoders/decoders** for common protocols. The JSON and
+  MessagePack implementations regularly
+  [benchmark](https://jcristharif.com/msgspec/benchmarks.html) as the fastest
+  options for Python.
+
+- 🎉 **Support for a wide variety of Python types**. Additional types may be
+  supported through
+  [extensions](https://jcristharif.com/msgspec/extending.html).
+
+- 🔍 **Zero-cost schema validation** using familiar Python type annotations. In
+  [benchmarks](https://jcristharif.com/msgspec/benchmarks.html) `msgspec`
+  decodes *and* validates JSON ~2x faster than
+  [orjson](https://github.com/ijl/orjson) can decode it alone.
+
+- ✨ **A speedy Struct type** for representing structured data. If you already
+  use [dataclasses](https://docs.python.org/3/library/dataclasses.html) or
+  [attrs](https://www.attrs.org),
+  [structs](https://jcristharif.com/msgspec/structs.html) should feel familiar.
+  However, they're
+  [10-100x faster](https://jcristharif.com/msgspec/benchmarks.html#benchmark-structs>)
+  for common operations.
+
+All of this is included in a
+[lightweight library](https://jcristharif.com/msgspec/benchmarks.html#benchmark-library-size)
+with no required dependencies.
+
+---
+
+`msgspec` may be used for serialization alone, as a faster JSON or
+MessagePack library. For the greatest benefit though, we recommend using
+`msgspec` to handle the full serialization & validation workflow:
+
+**Define** your message schemas using standard Python type annotations.
+
+```python
+>>> import msgspec
+
+>>> class User(msgspec.Struct):
+...     """A new type describing a User"""
+...     name: str
+...     groups: set[str] = set()
+...     email: str | None = None
+```
+
+**Encode** messages as JSON, or one of the many other supported protocols.
+
+```python
+>>> alice = User("alice", groups={"admin", "engineering"})
+
+>>> alice
+User(name='alice', groups={"admin", "engineering"}, email=None)
+
+>>> msg = msgspec.json.encode(alice)
+
+>>> msg
+b'{"name":"alice","groups":["admin","engineering"],"email":null}'
+```
+
+**Decode** messages back into Python objects, with optional schema validation.
+
+```python
+>>> msgspec.json.decode(msg, type=User)
+User(name='alice', groups={"admin", "engineering"}, email=None)
+
+>>> msgspec.json.decode(b'{"name":"bob","groups":[123]}', type=User)
+Traceback (most recent call last):
+  File "<stdin>", line 1, in <module>
+msgspec.ValidationError: Expected `str`, got `int` - at `$.groups[0]`
+```
+
+`msgspec` is designed to be as performant as possible, while retaining some of
+the nicities of validation libraries like
+[pydantic](https://pydantic-docs.helpmanual.io/). For supported types,
+encoding/decoding a message with `msgspec` can be
+[~2-80x faster than alternative libraries](https://jcristharif.com/msgspec/benchmarks.html).
+
+<p align="center">
+  <a href="https://jcristharif.com/msgspec/benchmarks.html">
+    <img src="https://raw.githubusercontent.com/jcrist/msgspec/main/docs/source/_static/bench-1.svg">
+  </a>
+</p>
+
+See [the documentation](https://jcristharif.com/msgspec/) for more information.
+
+
+## LICENSE
+
+New BSD. See the
+[License File](https://github.com/jcrist/msgspec/blob/main/LICENSE).

setup.py

@@ -74,10 +74,11 @@
     package_data={"msgspec": ["py.typed", "*.pyi"]},
     ext_modules=ext_modules,
     long_description=(
-        open("README.rst", encoding="utf-8").read()
-        if os.path.exists("README.rst")
+        open("README.md", encoding="utf-8").read()
+        if os.path.exists("README.md")
         else ""
     ),
+    long_description_content_type="text/markdown",
     python_requires=">=3.8",
     zip_safe=False,
 )