docs: Add Git page (#14582)

This PR adds a basic Git page to the docs so that we have somewhere to
link to from the Git upsell within Zed.

Release Notes:

- N/A

docs/src/SUMMARY.md

@@ -20,6 +20,7 @@
 - [Assistant Panel](./assistant-panel.md)
 - [Channels](./channels.md)
 - [Collaboration](./collaboration.md)
+- [Git](./git.md)
 - [Tasks](./tasks.md)
 - [Remote Development](./remote-development.md)
 - [REPL](./repl.md)

docs/src/git.md

@@ -0,0 +1,10 @@
+# Git
+
+Zed currently supports the following Git features:
+
+- Diff indicators in buffers and editor scrollbars
+- Git status in the project panel
+- Branch creating and switching
+- Git blame viewing
+
+More advanced Git features—like staging and committing changes or viewing history within Zed—will be coming in the future.