fix(lockfiles): unstage yarn.lock instead of ignoring it

[luftywiranda13]

PR Type

• Bugfix
• Feature
• Code style update (whitespace, formatting, missing semicolons, etc.)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other… Please describe:

Description

Based on facebook/create-react-app#2014 (comment). So in summary:

• remove package-lock.json from .gitignore because we already set package-lock=false in .npmrc
• but for yarn.lock I decided to always unstage it in pre-commit hook to prevent it to get merged in our repo.

How Has This Been Tested?

1. Install deps with npm/yarn
2. Try to commit
3. No generated package-lock.json, pre-commit hook always unstage yarn.lock

Screenshots (if appropriate):

N/A

Does this PR introduce a breaking change?

• Yes
• No

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the contributing.md.