[DOC] new icon assets resolution

[louisgv]

We now support more base icon name:

icon
icon512
icon-512
icon-512x512
icon1024
icon-1024
icon-1024x1024

As well as the production/development variant:

icon.production.png
icon.development.png

etc.etc....

See: PlasmoHQ/plasmo#172

[ColdSauce]

I'll add this into the docs depending on when we merge