Link checker parses headings inside component

[Eric-Arellano]

The link checker was failing to detect inline class methods (related to #2210) because it does not peek inside <Class> components.

To fix this, we now use our own parsing code for headings.

It's possible there will be future edge cases this PR does not account for in its heading parsing. Our link checker will fail in that case and we can forward fix.

[frankharkins]

Thanks! This solution looks good. Though if we hit more problems like this we might want to consider spinning up the server and making requests. It would be slower, but it'd be guaranteed correct.

[Eric-Arellano]

Though if we hit more problems like this we might want to consider spinning up the server and making requests. It would be slower, but it'd be guaranteed correct.

I don't think so - think about how slow checkPagesRender.ts is. It's important our link checker handles all historical API docs as well; the closed source link checker doesn't do that because its live render approach is too slow.