Feature: Support code language highlighting

[lytefast]

Adds support to highlight code for Kotlin, Python, Rust, XML, ProtoBuff. Kotlin has some additional support, but it wouldn't be hard to add it for other languages too.

Feature

New CodeRule + CodeNode added to the library.

• CodeNode does a bit of span-fu, see inlined documentation. Basically it makes sure that styles applied by the CodeNode apply first, then the child styles are applied. This prevents the CodeNode styles from overwriting the styles of the children.
• Nodes are passed in a CodeStyleProviders which provides it a way of creating styled spannables for the different values. This is how we can configure the styling in the client to use whatever styles we want.

Eventually this should support Textmate language extensions

Adding new language:

Adding simple support for new languages can be done by defining 3 things:

• line comment prefix
• built in types
• keywords

Example of adding a language:

val pythonRules = createGenericCodeRules<R, S>(
    codeStyleProviders,
    additionalRules = listOf(
        createSingleLineCommentPattern("#")
            .toFullMatchRule(codeStyleProviders.commentStyleProvider),
        Pattern.compile("""^@(\w+)""")
            .toFullMatchRule(codeStyleProviders.genericsStyleProvider)),
    definitions = arrayOf("class", "def", "lambda"),
    builtIns = arrayOf("True|False|None"),
    /* keywords */"from|import|global|nonlocal",
    "async|await|class|self|cls|def|lambda",
)

Additional changes

-New StyleNode.Text for a bit more optimized Node structure used for CodeNode

• added a basic BlockBackgroundNode similar to what we have in discord to the sample app

Screens

[lytefast]

I was tempted to change the render function here to do what Parent does, but didn't know if that would conflict with any downstream types.

[lytefast]

@AndyG renamted StyleNode.Text -> StyleNode.TextStyledNode in 09caf3a