Add final? 0.7.0 highlights and group by topic

[DragaDoncila]

References and relevant issues

Description

This PR adds sections for the remaining highlights for v0.7.0 and groups most highlights into sections:

New features & widgets:

• What's my metadata? napari-metadata to the rescue
• (Layer) Features galore
• Smarter new layer buttons
• Better text overlays

Rendering & display:

• More pixels to play with - texture tiling
• Points - any size you like

Performance:

• Lightning labels
• Grid mode -- bigger, better, faster
• Add & delete layers without delay
• Shapes layers -- select, zoom, delete, repeat

There are four entries that I couldn't figure out groups for:

• Transition to npe2
• Fixed camera angles
• Negative axis labels
• Infrastructure & dependencies

Would appreciate feedback on better grouping, if anyone has suggestions!

[brisvag]

Maybe note that this is not public for now cause we'r enot sure on the api.

[brisvag]

• Transition to npe2

• Fixed camera angles

• Negative axis labels

• Infrastructure & dependencies

I would put the top 3 in something like "Breaking changes". Let last one is fine at the bottom as an FYI.