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

[J. Ryan Stinnett via llvm-commits]

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@@ -0,0 +1,171 @@
+# llvm-debuginfo-analyzer
+
+These are the notes collected during the development, review and test.
+They describe limitations, know issues and future work.
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jryans wrote:

```suggestion
They describe limitations, known issues and future work.
```

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