[llvm] [llvm][Docs] Expand MyFirstTypoFix's post-commit section (PR #79827)

[David Spickett via llvm-commits]

DavidSpickett wrote:

This uses content from https://github.com/llvm/llvm-project/pull/78292, so if/when this lands, I'll update that PR to be a much smaller comment that links to this new documentation.

https://github.com/llvm/llvm-project/pull/79827