Icon property for blocks

Since Logseq is more around blocks and pages are just collections of blocks with a name I think it would be nice to have the icon:: property for blocks too.

I suggest to render it as the bullet point of the block:

IMG_20220711_111520_963-01

There is need for some effect for collapsed blocks though.

Also, it would be better if the icon:: ... line is not displayed when not editing a block (like title:: for pages).