Load icons postLCP

[ryanmparrish]

Hello, I have a draft PR that moves our loadIcons() function to postLCP and I am opening this discussion to see if this is needed and viable or if we need to re-factor this task and requirements [3]. Here are the details.

We/I initially thought this change would improve our page load LCP, however the impact appears to be marginal and it actually introduces some complex CLS issue since the icon DOM area size scales based on the relative font size it's relative to.

My gut tells me this is one step forward and two steps back.

1. Is this a viable need?
2. Any issues, concerns or suggestions on the approach i've taken.
3. The elephant in the room, the Icons should likely be refactored and served from a federal level and allow authors to add to icon sets and automate the library offering. This work above may be better introduced w/ that task.
   I had done some previous work on expanding out icon set w/ the full S1 and S2 icon sets. [https://rparrish-icons-libs--milo--adobecom.hlx.page/drafts/rparrish/icon/icons-libs], however this task got put on hold when ran into a CORS issue w/ consuming site and I was going to wait for milo to adopt HLX5 to address this, this actual adoption HLX5 timeline is pretty far out still and after some conversations w/ @mokimo - The suggested direction was to tackle this from the federal repo for all consuming sites to use.