[llvm] [llvm-debuginfo-analyzer][DOC] Convert 'README.txt' to markdown. (PR #86394)

[Carlos Alberto Enciso via llvm-commits]

CarlosAlbertoEnciso wrote:

> ⚠️ We detected that you are using a GitHub private e-mail address to contribute to the repo. Please turn off [Keep my email addresses private](https://github.com/settings/emails) setting in your account. See [LLVM Discourse](https://discourse.llvm.org/t/hidden-emails-on-github-should-we-do-something-about-it) for more information.

Fixed.

https://github.com/llvm/llvm-project/pull/86394