[clang-tools-extra] [llvm] [clang-tools-extra][docs] Convert maintainers file to Markdown (PR #200365)

[David Spickett via cfe-commits]

DavidSpickett wrote:

Sorry, I jumped the gun. For what it's worth, my motivation was seeing someone ask on Discord which file to use, and I thought it having an odd one out was not ideal. The RFC was a reminder to do this change, but I wasn't trying to push for either side of that.

I didn't actually include that motivation though, which was a mistake, I should have.

My only concern was the maintainer files, so I don't plan to make any more changes.

https://github.com/llvm/llvm-project/pull/200365