Consider removing the `variant` property on `Text` in favor of just using Markdown

Currently, Markdown allows you to specify H1, H2, H3 etc through `# Heading 1` etc, but we also redundantly provide a `variant` parameter for this.

How about we remove this redundancy? It's awkward to implement also. What if we have a `h1` variant Text, with `#### Subtitle` in it? Which level is that heading?