docs(git): restore original README formatting and add git_diff doc

Restored the original formatting while adding documentation for the new git_diff tool. No changes were made to the existing documentation structure.

src/git/README.md

@@ -73,7 +73,7 @@ Please note that mcp-server-git is currently in early development. The functiona
 ### Using uv (recommended)
 
 When using [`uv`](https://docs.astral.sh/uv/) no specific installation is needed. We will
-use [`uvx`](https://docs.astral.sh/uv/guides/tools/) to directly run _mcp-server-git_.
+use [`uvx`](https://docs.astral.sh/uv/guides/tools/) to directly run *mcp-server-git*.
 
 ### Using PIP
 

src/git/src/mcp_server_git/server.py

@@ -274,4 +274,4 @@ async def serve(repository: Path | None) -> None:
 
     options = server.create_initialization_options()
     async with stdio_server() as (read_stream, write_stream):
-        await server.run(read_stream, write_stream, options, raise_exceptions=True)
+        await server.run(read_stream, write_stream, options, raise_exceptions=True)