Add RichText component

[ericluap]

Adds a basic RichText component. Closes #654

It also adds a simple example.

Having different font sizes causes problems with alignment. alignItems(`Baseline) would solve this but I don't think that currently exists here.

[ericluap]

The way I'm doing this seems a bit foolish as every tree concatenation eventually becomes a list concatenation in the toList function. How can I avoid doing this? I'll keep working on it.

[glennsl]

Awesome @SirFurness! The code looks mostly great, but I do have a few general suggestions:

• It would be nice to have a separate RichTextmodel that is not bound to the component, so that rich text can be manipulated without bringing in the whole UI layer, and even so that alternative renderers may be implemented. We might want to have one that can embed rich text using immediate mode in a <Canvas> for example.

• It would also be nice to have a DSL for creating rich text. Something like RichText.(text(~family="Arial", "Hello ") ++ text(~size=24, "world") |> color(Colors.red)). That is, to be able to optionally set properties at creation, and also be able to set them across a span of text nodes.

• You might want/have to adapt this to feat(components): move font styling out of Style and use families #879

[glennsl]

Nice! Aside from a few stylistic suggestion below, I have a couple more general suggestions:

• As a user, RichTextModel is what you're mostly going to use to work with the model. The component is just used to render the end result. Therefore it seems more convenient to rename RichTextModel to RIchText and the component to RichTextView so that the one that's most frequently used is also the shortest and most convenient to use.

• The model isn't really UI-specific (or specific to this UI). Could it be moved to Core instead?

• It would be great to have an interface file for RichTextModel.

[ericluap]

I tried moving RichText to Core but it creates a dependency cycle.

RichText depends on Font which depends on Core.

[glennsl]

I tried moving RichText to Core but it creates a dependency cycle.

RichText depends on Font which depends on Core.

Ah, I see, that's unfortunate. Thanks for trying though!

[glennsl]

Awesome, looks good to me now at least!

[glennsl]

Thanks for doing an awesome job with this @SirFurness! 🎉

[lessp]

ping @thangngoc89 😄