Update pre-commit hook

[xl4624]

Addresses #38 by using git diff --staged --name-only to only add staged files to the commit.

Caveat here is that npm run lint:fix and npm run format will still run for all files in the working directory. Tried fixing it by passing the staged files in git diff --staged --name-only to the linters/formatters, but unfortunately passing specific files with xargs will throw an error to file types that aren't recognized like No parser could be inferred for file: .husky/pre-commit. Also tried stashing untracked/unstaged files with git stash push -k -u before linting and git stash pop after but that seemed very error prone.