Handle link click in editor

[Wavesonics]

I don't think this is ready to merge yet, but take a look at the current approach.

I added a new listener: RichSpanClickListener

Which gets clicks on all RichSpans, and lets the user sort them out.

I have an example in RichEditorContent.kt using this new listener to show a popup simulating a spellchecker.

However getRichSpanByOffset() only seems to work in the BasicRichTextEditor, The Outline variant which I think has extra padding maybe? The clicks return the wrong span. It appears to me to be offset by maybe the amount of padding? Not sure.

In order to make all of this work I had to make more classes public, which might be fine? But if we decide we don't want to expose all of those internal workings, maybe we'd have some stripped down classes to return instead in the click listener?

[Wavesonics]

I got this working again

however it suffers from the same problem as outlined in #421

So if there is line wrapping, then it will select the wrong span of text.

The bug is separate from this PR, so I think this is ready for review now.

I had to make some decisions because of the new strict API checking on what to make public VS internal, so not sure what you think about the choices I made there. Importantly, RichSpanStyle needs to be a public, open, class now so that custom spans can be applied.

[Wavesonics]

Okay, I'm understanding the code base quite a bit better than before, I refactored things so I no longer have to make RichParagraph or RichSpan public.

[Wavesonics]

Just rebased this to get the line-wrapping fix #436

But the issue with OutlinedRichTextEditor click offsets being incorrect appears to remain.

[Wavesonics]

Ha never mind, I think I fixed the OutlinedRichTextEditor issue! Just had to correct for ContentPadding