chore: restructure pre-commit and clarify instructions on fixing existing changes

Following on from some discussions in Holberton team, where there's been some confusion about the initial steps to get pre-commit set-up on an existing project I've had an attempt at clarifying the instructions. This includes:

• restructuring to make more explicit that you should have a set of standard hooks, plus some language-specific checks
• more detail on why running pre-commit run --all-files is helpful, particularly in the context of CI
• adding a .git-blame-ignore-revs file

assigned to @sw2187

added 121 commits

• cbef63d5...b0d6f128 - 120 commits from branch master
• 25c99bd3 - chore: restructure pre-commit and clarify instructions on fixing existing changes

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