feat: support toRegex and toRegexString with restrictions (#1)

* feat: support toRegex and toRegexString with restrictions

* docs: add README

.github/workflows/build.yml

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+name: Build project
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v1
+      - name: Install Node.js 10
+        uses: actions/setup-node@v1
+        with:
+          node-version: 10
+      - name: Setup cache
+        uses: bahmutov/npm-install@HEAD
+      - name: Install dependencies
+        run: npm t
+      - name: Test and build code
+        run: npm run validate
+      - name: Upload test reports
+        uses: codecov/codecov-action@v1
+      - name: Semantic Release
+        uses: cycjimmy/semantic-release-action@v2
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
+        with:
+          branches: |
+            [
+              'master',
+              {
+                name: 'beta',
+                prerelease: true
+              }
+            ]

.gitignore

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+.DS_Store
+coverage
+dist
+node_modules

.npmrc

@@ -0,0 +1 @@
+save-exact=true

.prettierrc.js

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+module.exports = require('kcd-scripts/prettier')

README.md

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+# super-expressive.macro
+
+A macro to generate regular expressions at build-time with super-expressive.
+
+[![version][version-badge]][package] [![MIT License][license-badge]][license]
+[![All Contributors](https://img.shields.io/badge/all_contributors-1-orange.svg?style=flat-square)](#contributors)
+
+> You may like to watch
+> [this YouTube video](https://www.youtube.com/watch?v=1queadQ0048&list=PLV5CVI1eNcJgCrPH_e6d57KRUTiDZgs0u)
+> to get an idea of what macros are and how to use them.
+
+## Motivation
+
+[Super Expressive](https://github.com/francisrstokes/super-expressive) is
+awesome, but it's a runtime library only.
+
+Depending on the use case, Super Expressive is very useful for declaring the
+regular expressions, but when building the project, the final expression is
+preferred.
+
+This library aims to be a drop-in replacement for Super Expressive where
+applicable - see [restrictions](#restrictions).
+
+## Installation
+
+`npm install super-expressive.macro`
+
+`yarn add super-expressive.macro`
+
+> This library depends on `super-expressive`. Please make sure to install it.
+
+## Usage
+
+To use macros, make sure to
+[set up `babel-plugin-macros`](https://github.com/kentcdodds/babel-plugin-macros/blob/main/other/docs/user.md).
+
+## Example
+
+```js
+import SuperExpressive from 'super-expressive.macro'
+
+const myRegex = SuperExpressive()
+  .startOfInput.optional.string('0x')
+  .capture.exactly(4)
+  .anyOf.range('A', 'F')
+  .range('a', 'f')
+  .range('0', '9')
+  .end()
+  .end()
+  .endOfInput.toRegex()
+```
+
+After compilation:
+
+```js
+const myRegex = /^(?:0x)?([A-Fa-f0-9]{4})$/
+```
+
+> Notice that the macro import disappeared after compilation
+
+Check the
+[`super-expressive`'s detailed API](https://github.com/francisrstokes/super-expressive/#api)
+for more examples. Don't forget to check the [restrictions](#restrictions).
+
+## Restrictions
+
+Because this plugin runs at build-time, there are some restrictions to its
+usage.
+
+- You can't use dynamic variables inside the macro, all the params to its
+  methods must be literals;
+- You can't use constant variables inside the macro at the moment but
+  [there's an issue](https://github.com/arthurdenner/super-expressive.macro/issues/2)
+  to track if this is possible as we improve this macro;
+- You can't use [subexpressions] inside the macro at the moment but
+  [there's an issue](https://github.com/arthurdenner/super-expressive.macro/issues/3)
+  to track if this is possible as we improve this macro;
+
+## Contributors
+
+Thanks goes to these wonderful people
+([emoji key](https://github.com/kentcdodds/all-contributors#emoji-key)):
+
+<!-- ALL-CONTRIBUTORS-LIST:START - Do not remove or modify this section -->
+<!-- prettier-ignore-start -->
+<!-- markdownlint-disable -->
+
+<!-- markdownlint-enable -->
+<!-- prettier-ignore-end -->
+
+<!-- ALL-CONTRIBUTORS-LIST:END -->
+
+This project follows the
+[all-contributors](https://github.com/kentcdodds/all-contributors)
+specification. Contributions of any kind welcome!
+
+## LICENSE
+
+MIT
+
+[license-badge]:
+  https://img.shields.io/npm/l/super-expressive.macro.svg?style=flat-square
+[license]:
+  https://github.com/arthurdenner/super-expressive.macro/blob/master/LICENSE
+[version-badge]:
+  https://img.shields.io/npm/v/super-expressive.macro.svg?style=flat-square
+[package]: https://www.npmjs.com/package/super-expressive.macro