docu: introduces doxygen-awesome-css

.reuse/dep5

LICENSES/MIT.txt

doc/Doxyfile

doc/doxygen-awesome-css/doxygen-awesome-darkmode-toggle.js

...xygen-awesome-css/doxygen-awesome-fragment-copy-button.js

doc/doxygen-awesome-css/doxygen-awesome-interactive-toc.js

doc/doxygen-awesome-css/doxygen-awesome-paragraph-link.js

...some-css/doxygen-awesome-sidebar-only-darkmode-toggle.css

doc/doxygen-awesome-css/doxygen-awesome-sidebar-only.css

doc/doxygen-awesome-css/doxygen-awesome-tabs.js

doc/doxygen-awesome-css/doxygen-awesome.css