Cleanup: cargo fmt max comment length

[orbitalturtle]

Throughout lndk the comment lengths are all over the place. This PR establishes a standard comment length maximum of 100, which is the same max line length as the rest of the code. The PR also updates the github workflows to enforce this new standard.

Contributors now will need to run cargo fmt -- --config unstable_features=true --config wrap_comments=true --config comment_width=100 to make sure comments meet this restriction.

We also sneak in a couple other fixes in this PR:

• Update codecov-actions to v4 to fix #114
• Add .vscode to .gitignore

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 0.00%. Comparing base (4d2d513) to head (27df32b). Report is 24 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #113 +/- ## ====================================== Coverage 0.00% 0.00% ====================================== Files 1 1 Lines 40 77 +37 ====================================== - Misses 40 77 +37 ```

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