feat: youtube alt

[Omikorin]

This PR adds very popular Youtube alternative style.

The example of another website using it can be seen here.

That's how it looks on light theme:

and dark:

---

It's simply a red color but has bad WCAG status. We could change it a little bit to be more compatible.

#FF0000 example:

The first possible solution is #EB0000:

Full WCAG compatibile option doesn't look like Youtube #B30000:

So, I suggest using #E60000 as it is a bit darker than the minimal solution and I found it optimal for me too.

Let me know what do you think, then I'll update the PR.

[sethcottle]

@Omikorin thanks for this PR! Sorry for the delay on getting to this—took a little time for the holidays. The #FF0000 isn't optimal, but my general rule of thumb is not to tweak brand colors and use them to the best they're able to be, which isn't always accessible. There are a few branded buttons within LittleLink that fail contrast checks, and that's just a symptom of is what it is with the brand colors IMO. I'm going to go ahead and merge this in since this is generally a common alternative with this color scheme!