Update doxygen CSS

[2bndy5]

This also upgrades to doxygen to v1.11.0 which now supports github-style admonitions.

Basically, we can write the following in markdown:

> [!note]
> is translated to `\note`

> [!warning]
> is translated to `\warning`

> [!tip]
> is translated to `\remark`

> [!caution]
> is translated to `\attention`

> [!important]
> is translated to `\important`

and it will render in doxygen and github as admonitions:

Note

is translated to \note

Warning

is translated to \warning

Tip

is translated to \remark

Caution

is translated to \attention

Important

is translated to \important

However, these special blockquotes are root-level syntax only. Meaning you cannot nest these admonitions in other block elements (like list items). This limitation is due to commonmark specifications and is observed in both github and doxygen output.