[clang] [clang] Add sections to C++ DR status page (PR #165749)

[Richard Smith via cfe-commits]

https://github.com/zygoloid approved this pull request.

Thanks, [looks nice](https://html-preview.github.io/?url=https://github.com/Endilll/llvm-project/blob/819b506d53f6c5e6de6b2369e66c93d08f9208c8/clang/www/cxx_dr_status.html).

https://github.com/llvm/llvm-project/pull/165749