[LLSC-38] Add extensions recs and settings json to backend folder

[mslwang]

Notion ticket link

Add VSCode settings json to backend

Implementation description

Adding settings json for people who work predominantly in the backend folder, ie. their workspace is /backend. The language server isn't able to pick up the python executable in .venv on /backend within this json file without having it included in /backend.

Steps to test

1. Go to VSCode and open the project from /backend.
2. Check if the interpreter is set to .venv/bin/python and you're able to see autocomplete and hover text and signature information.

Checklist

• My PR name is descriptive and in imperative tense
• My commit messages are descriptive and in imperative tense. My commits are atomic and trivial commits are squashed or fixup'd into non-trivial commits
• I have run the appropriate linter(s)
• I have requested a review from the PL, as well as other devs who have background knowledge on this PR or who will be building on top of this PR