includes:
- update Makefile: build html output; src/build dir
- move spec src to src dir
- remove image dir and pull in riscv logo from docs-resource submodule
- update docs-resources submodule to latest
- add pre-commit hooks and GH action to run it
- add GOVERNANCE and MAINTAINERS file templates
- update README pull in new sections
- remove generated PDF
- .gitignore the build dir
- modify attribute cfg in header.adoc to match build/src dir; logo image

Signed-off-by: Kevin Broch <kbroch@rivosinc.com>