feat: Create flame_markdown

[luanpotter]

Description

Add a bridge package flame_markdown to the markdown package to allow for easily creating TextElementComponents (or TextNodes in general) using the markdown syntax.

This will vastly facilitate working with rich text, specially for simple formatting like bold and italics, without requiring the user to manually specify the node tree structure.

Checklist

• I have followed the Contributor Guide when preparing my PR.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• I have updated/added relevant examples in examples or docs.

Breaking Change?

• Yes, this PR is a breaking change.
• No, this PR is not a breaking change.

[spydon]

Niiice! I believe this was what @st-pasha had in mind when he created the text rendering system you've been fiddling with now.

[luanpotter]

That is my theory as well, as both structures line up pretty nicely.
This coming full circle will be insanely helpful for some of my games.
I only hope, if one day @st-pasha ever blesses us again with his presence in the realms of the living, that my followup can live up to his expectations 🙇

[spydon]

Wow, so simple, love it!