I recently had a chance to try Live Share in VSCode - a kind of Google Docs for collaborative work with code.
After logging in via GitHub or a Microsoft account with this extension, you can start a “Live session” and send your colleague a link.
Your colleague connects to the session and gets access to the project files from his editor (with his customized hotkeys): VSCode or Visual Studio.
It’s not perfect but it’s good enough to use.
As an add-on, extensions are offered to add chat and audio communication.
Since March they are testing the connection to the Live Share session from the browser.
Introductory video and description: