`color::` property for blocks

Make the color:: property change the text color of the block. (The highlight color is already easy to change).

Perhaps even creating a text-color:: property to avoid confusion with background-color::

Btw, If there’s some interest, I’ll try implementing it myself. As a functional programmer, I’ve been wanting to learn Clojure for quite some time.

Related questions and issues:

Ended up doing my first PR to logseq!