Add Doxygen Awesome CSS theme

[rmisev]

Add the Doxygen Awesome Base Theme and the following extensions:

• Dark Mode Toggle
• Fragment Copy Button
• Paragraph Linking

More info:

• https://jothepro.github.io/doxygen-awesome-css/
• https://jothepro.github.io/doxygen-awesome-css/md_docs_2extensions.html

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (28bc95e) 99.72% compared to head (d4e9af4) 99.72%. Report is 2 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #17 +/- ## ======================================= Coverage 99.72% 99.72% ======================================= Files 15 15 Lines 2215 2217 +2 ======================================= + Hits 2209 2211 +2 Misses 6 6 ``` | [Files](https://app.codecov.io/gh/rmisev/url_whatwg/pull/17?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Rimas+Misevi%C4%8Dius) | Coverage Δ | | |---|---|---| | [include/upa/url.h](https://app.codecov.io/gh/rmisev/url_whatwg/pull/17?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Rimas+Misevi%C4%8Dius#diff-aW5jbHVkZS91cGEvdXJsLmg=) | `99.74% <100.00%> (+<0.01%)` | :arrow_up: | | [include/upa/url\_host.h](https://app.codecov.io/gh/rmisev/url_whatwg/pull/17?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Rimas+Misevi%C4%8Dius#diff-aW5jbHVkZS91cGEvdXJsX2hvc3QuaA==) | `100.00% <100.00%> (ø)` | | | [include/upa/url\_percent\_encode.h](https://app.codecov.io/gh/rmisev/url_whatwg/pull/17?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Rimas+Misevi%C4%8Dius#diff-aW5jbHVkZS91cGEvdXJsX3BlcmNlbnRfZW5jb2RlLmg=) | `100.00% <100.00%> (ø)` | |

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