Docs skeleton (#51)

* Add doxygen-awesome-css submodule

* Basic documentation files

- conf.py: run by sphinx
- about.md: info about rocprofiler
- features.md: overview of features
- installation.md: build/test/install instructions
- index.md: sets up main page
- generate-doxyfile.cmake: generates rocprofiler.dox with rocprofiler-specific info
- environment.yml: conda environment
- Makefile: sphinx makefile
- README.md: build instructions
- rocprofiler.dox.in: doxygen template
- .gitignore: ignores generated files
- .nojekyll: prevents GitHub Pages from using Jekyll for deployment of pages

* Documentation scripts

- scripts for doing common sequences of commands for building docs
- update-docs.sh: builds the docs and installs the docs if /docs directory is present
- update-doxygen.sh: quick script for generating doxygen

* Workflow for docs

- step for building docs
- step for deploying docs

* Update doxygen comments in include/rocprofiler

- rocprofiler.h / rocprofiler_plugins.h
  - fixed non-existent global references in doxygen comments
  - fixed parameter names that were incorrect or not updated

* Update docs workflow

- only deploy docs when on main branch

.gitmodules

@@ -7,3 +7,6 @@
 [submodule "fmt"]
 	path = external/fmt
 	url = https://github.com/fmtlib/fmt.git
+[submodule "source/docs/doxygen-awesome-css"]
+	path = external/doxygen-awesome-css
+	url = https://github.com/jothepro/doxygen-awesome-css.git