Autocomplete docs (#3126)

Release Notes:

- Added documentation display for autocomplete items.
- Fixed autocomplete filtering blocking the Zed UI, causing hitches and
input delays with large completion lists.
- Fixed hover popup link not firing if the mouse moved a slight amount
while clicking.
- Added support for absolute path file links in hover popup and
autocomplete docs.

crates/language/Cargo.toml

@@ -45,6 +45,7 @@ lazy_static.workspace = true
 log.workspace = true
 parking_lot.workspace = true
 postage.workspace = true
+pulldown-cmark = { version = "0.9.2", default-features = false }
 regex.workspace = true
 schemars.workspace = true
 serde.workspace = true