Add cachetools and new type checkers

[delaaxe]

What is this Python project?

• cachetools is a chaching library.
• pyre, pytype and pyright are type checkers

What's the difference between this Python project and similar ones?

• cachetools is a library for cached collections which is different from the current items under caching.
• the new typechekers each have different pros and cons compare to mypy so it's valuable to have them all listed so users can decide which one's the best for them
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Anyone who agrees with this pull request could vote for it by adding a 👍 to it, and usually, the maintainer will merge it when votes reach 20.