Custom search icon

[MGaetan89]

Is your feature request related to a problem? Please describe

Dokka allows customizing its icons using the customAssets configuration option: https://kotlinlang.org/docs/dokka-html.html#customize-assets
However, the search icon used in the top bar is not listed: https://github.com/Kotlin/dokka/tree/1.9.20/dokka-subprojects/plugin-base/src/main/resources/dokka/images

The first icon is theme-toggle.svg, but the second is not listed.

Describe the solution you'd like

The search icon can be customized using customAssets.from("search-icon.svg") (using Dokka 2.0 syntax).

Describe alternatives you've considered

None.

Additional context

I'm using Dokka 2.0.0-Beta, but this is probably relevant for Dokka 1.9 too.