docs: Add documentation to a subset of available extensions (#24138)

I was able to use my experience with some of the Deno extensions to
flesh out their documentation a bit

I've provided docs for the following:
- web
- fetch
- net
- webidl
- url
- io
- crypto
- console

---------

Signed-off-by: Richard Carson <Rscarson@rogers.com>

1 files changed, 22 insertions, 2 deletions

diff --git a/ext/io/README.md b/ext/io/README.md
index b66dda76e..3aef61b0b 100644
--- a/ext/io/README.md
+++ b/ext/io/README.md
@@ -1,4 +1,24 @@
 # deno_io
 
-This crate provides IO primitives for other Deno extensions, this includes stdio
-streams and abstraction over File System files.
+**This crate provides IO primitives for other Deno extensions, this includes
+stdio streams and abstraction over File System files.**
+
+## Usage Example
+
+From javascript, include the extension's source:
+
+```javascript
+import * as io from "ext:deno_io/12_io.js";
+```
+
+Then from rust, provide:
+`deno_io::deno_io::init_ops_and_esm(Option<deno_io::Stdio>)` in the `extensions`
+field of your `RuntimeOptions`
+
+Where `deno_io::Stdio` implements `Default`, and can therefore be provided as
+`Some(deno_io::Stdio::default())`
+
+## Dependencies
+
+- **deno_web**: Provided by the `deno_web` crate
+- **deno_tty**: Provided in `deno/runtime/ops/tty.rs`