clang-change-namespace tool is not documented

[LegalizeAdulthood]

Bugzilla Link	36171
Version	unspecified
OS	Windows NT

Extended Description

clang-change-namespace tool is present in the repository, but is not documented anywhere.

[llvmbot]

@llvm/issue-subscribers-good-first-issue

[snowmang1]

hello, is this adding documentation to the clang-tools-extra/docs docs or is this ticket wanting a more commented section within clang-change-namespace itself? If the former is true do I just add to the doxygen documentation files?
thank you for the clarification