Update library metadata descriptions

[helms-charity]

Using the boilerplate blocks, copy those descriptions into our corresponding blocks to set us up for the ExMod tool.
https://main--biomarkerboost--aemdemos.aem.page/tools/sidekick/library.html?plugin=blocks

However, for blocks that have more than 1 variant, you'll need to add some description of what makes that variant different than the others.

Also: We need good descriptions for ccheaderslider and heritage-hero-cc