Cardmeta improvements

[asinghvi17]

Documenter pipeline to move cardmeta blocks

Add a Documenter.jl pipeline to move cardmeta blocks down to the end of the page, unless the block specifies otherwise.

This would be a kwarg force=true.

In general this would have to happen at the very initial stages, before even TrackHeadings, and if we're parsing the cardmeta block anyway then we may as well add the heading if it exists. If there is a specified title then it's easy, if not then we can just rely on autocomplete in any case.

SVG support

What it says on the tin. We may want to refactor cover to hold the actual figure, and show lazily.

Auto title detection

If no title is detected, fall back to the page name.

Indicate backend and image type preference for figure blocks.

• This would be injected into the page meta at parse time in the initial Documenter pipeline.
• The figure block can check page.meta for defaults, we can use Arrow namespacing like MAKIE:Backend, MAKIE:Type, MAKIE:screen_kws.