Make feature and type status emojis more accessible

[amoeba]

When we show support for a feature or type in driver doc pages, we show an emoji. Bare emoji are a bit too vague I think and we could add title attributes and even add a key to the generated report.

The emojis we're currently using are:

• ✅ for "this is supported"
• ⚠️ for "this is partially supported, see footnote next to me"
• ❌ for "this is not supported"

[lidavidm]

A badge might be good. (We might have to switch to generating HTML; also I don't recall if MyST allows nesting Markdown inside HTML)