Fix windows specific diff viewing issue

We were naively using fsPath which transforms path using backslash separators. This caused a OS specific issue when "Windows" was detected from the user agent.

Screenshots

1. Emulate a windows user agent
2. Make a change to any file.
3. Click on the file in the Source Control tab.
4. The diff should show up 👍

Before	After

How to emulate a windows user agent

• In Chrome add a "Windows" device by going to Settings > Devices > Add custom device
• The only important thing to set here is the User agent string

Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/108.0.0.0 Safari/537.36

Example screenshot

• Then click Toggle Device Toolbar and select your new "Windows" device.

Example screenshot