Feature Idea: Conflict Marker detection and reporting in source files

As so helpfully pointed out by @phadej, Clang is able to produce a helpful report when detecting version control conflict markers in a source file:

I believe it would be a welcome addition from our users, and would certainly help with GHC's reputation to the general public.

Here are relevant links from the clang source file:

• Lexer.cpp#L4028-L4032
• Lexer.h#L42-L55
• Lexer.cpp#L3077-L3156
• DiagnosticLexKinds.td#L97