chore: update readme to include run instructions (#23)

* chore: update readme to include run instructions

* fix: type error on latest deno version

README.md

@@ -7,6 +7,10 @@
 
 Python interpreter bindings for Deno.
 
+## Example
+
+Import any locally installed Python package, for example, `matplotlib`:
+
 ```ts
 import { python } from "https://deno.land/x/python@0.2.0/mod.ts";
 
@@ -20,6 +24,14 @@ plt.plot(xpoints, ypoints);
 plt.show();
 ```
 
+When running, you **must** specify `--allow-ffi`, `--allow-env` and `--unstable`
+flags. Alternatively, you may also just specify `-A` instead of specific
+permissions since enabling FFI effectively escapes the permissions sandbox.
+
+```shell
+deno run -A --unstable <file>
+```
+
 ## Documentation
 
 Check out the docs
@@ -29,29 +41,24 @@ Check out the docs
 
 This module uses FFI to interface with the Python interpreter's C API. So you
 must have an existing Python installation (with the shared library), which is
-something like `python39.dll`, etc.
+something like `python310.dll`, etc.
 
 Python installed from Microsoft Store does not work, as it does not contain
 shared library for interfacing with Python interpreter.
 
 If the module fails to find Python, you can add the path to the Python in the
 `DENO_PYTHON_PATH` environment variable.
 
+`DENO_PYTHON_PATH` if set, must point to full path including the file name of
+the Python dynamic library, which is like `python310.dll` (Windows),
+`libpython310.dylib` (macOS) and `libpython310.so` (Linux) depending on
+platform.
+
 ## Maintainers
 
 - DjDeveloper ([@DjDeveloperr](https://github.com/DjDeveloperr))
 - Elias Sjögreen ([@eliassjogreen](https://github.com/eliassjogreen))
 
-## Permission Table
-
-| Permission Needed | Reason                                         |
-| ----------------- | ---------------------------------------------- |
-| `--allow-env`     | For finding the location of the python library |
-| `--allow-run`     | For finding the location of the python library |
-| `--allow-read`    | For reading the library                        |
-| `--allow-ffi`     | It uses FFI to interact with python            |
-| `--unstable`      | It's unstable because it uses FFI              |
-
 ## Other
 
 ### Contribution

src/python.ts

@@ -135,7 +135,7 @@ export function kw(
  * ```
  */
 export class Callback {
-  unsafe: Deno.UnsafeCallback;
+  unsafe;
 
   constructor(public callback: PythonJSCallback) {
     this.unsafe = new Deno.UnsafeCallback(