doxygen content should be styled to look the same as sphinx docs

[wmamills]

For the 2023.04 release we plan to integrate doxygen content.
However, at that time they style of the doxygen sub-site will still be the default doxygen style and does not mesh will visually or functionally with the sphinx docs.

For 2023.10 release we should update the doxygen subsite to look similar to the sphinx docs matching visual styles and moving from the top menu format to sidebar format like the sphinx docs.

(This issue can be canceled if we choose to eliminate the doxygen sub-site and rely wholiny on breathe integration into the sphinx visible TOC.)

[wmamills]

Note to self: People recommend pipewire as well done doxygen integration
https://docs.pipewire.org/group__pw__stream.html

[wmamills]

Note to self: Zephyr appears ro be using this:
https://jothepro.github.io/doxygen-awesome-css/index.html

[wmamills]

PR #26 does this.

[wmamills]

Close with merge of PR #26