Copy for new splash page (need help with JSX syntax to incorporate the new graphics)

[bumblefudge]

this is my least favorite thing about docusaurus...

To be clear, I opened this PR to provide copy for a redesign of our splash page that would link directly to multiple different "starting points" in the docs, but my feeble brain cannot understand JSX so someone who knows that syntax could really help this become mergeable with or without new image assets :D

Todo:

• fix JSX to display links to multiple "Getting started" pages on homepage, without new images
• OPTIONAL - add images!
• figure out sidebar logic to add more navigable links. In this commit I added some helpful cross-links to the bottom of the Issuer and Verifier getting starting pages, but it would be much more usable if the same links were added as links to the sidebar of the Issuer and Verifier sections. I couldn't figure out the layered autogeneration+custom-links Sidebar logic in the docusaurus docs tho, and had to prioritize other work.

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Name	Status	Preview	Updated
verity-demo-site	✅ Ready (Inspect)	Visit Preview	Oct 20, 2022 at 10:49AM (UTC)
verity-docs	❌ Failed (Inspect)		Oct 20, 2022 at 10:49AM (UTC)

[bumblefudge]

I also seem to have bungled the relative link to the new asset... oof.