[Feature] Add Basic Git Integration

[ab-613]

Description

The Git icon is present in the activity bar, but clicking it does nothing. We need a way to view diffs and perform basic Git operations within the WebContainer.

Tasks

• Create a "Source Control" view tab in the sidebar. (will need logic for tab switching from the file exporer and vice versa).
• Implement git status and git diff visualization. (not desperately needed, but would make a big "diff" ;) )
• Able to commit changes and push to remotes.