Support gemini URI-Scheme (gemini://)

#### Is your feature request related to a problem? Please describe.
When someone sends a gemini URI, I cannot click on it so that a gemini browser will open that link. At the moment I always have to copy the gemini URI and then I'll have to paste it into my gemini browser.

#### Describe the solution you'd like.
I'd like that the gemini-URI gets highlighted the same way as it is done for `https://` links. I'd like that I can click on the URI and then my preferred gemini-client will open the gemini-URI. An example URI would look like this: `gemini://gemini.circumlunar.space/`

#### Describe alternatives you've considered.
I think there are no alternatives than highlighting `gemini://`-URIs.

#### Additional context
Here you'll find some more information about the gemini-protocol: https://gemini.circumlunar.space/

For element-web there also exists a similar issue: https://github.com/vector-im/element-web/issues/15018