[NFC] As part of using inclusive language within the llvm project, this patch replaces master with main when referring to `.chm` files. Reviewed By: teemperor Differential Revision: https://reviews.llvm.org/D113299
Differential Revision: https://reviews.llvm.org/D79065
Differential Revision: https://reviews.llvm.org/D77473
Add basic doxygen config following clang and llvm example with minimal changes.