Links to channel notes (#7262)

Release Notes:

- Added outline support for Markdown files
- Added the ability to link to channel notes:
https://zed.dev/channel/zed-283/notes#Roadmap

crates/zed/Cargo.toml

@@ -57,6 +57,7 @@ image = "0.23"
 indexmap = "1.6.2"
 install_cli = { path = "../install_cli" }
 isahc.workspace = true
+itertools = "0.11"
 journal = { path = "../journal" }
 language = { path = "../language" }
 language_selector = { path = "../language_selector" }