Add Doxygen and Clang to Actions

[brentru]

• Adding clang-and-doxy step now that the repo is public, addressing Enable deploy script for Doxygen when repository is public #55

Noting that this library utilizes a Doxygen file in the root directory to exclude doxygening the protocol buffer stubs and support headers.

[brentru]

Updated CI script to build for S2, Doxy in-order.