ESC Concepts page copy refresh for messaging

[thoward]

ESC Concepts section in general needs development.

First step is just to spruce up existing landing page and how it works page. Reach out to Gavin, who has some ideas on how to improve these, do a review of the two pages and make appropriate edits. These changes are a short term stop-gap.

Second step is to scale up the Concepts section of docs similar to the Pulumi IaC Concepts with a much more detailed/deeper exploration of ESC concepts. Reach out to Cleve to discuss and build an IA content plan. Produce a Google Doc for this plan.

This ticket tracks both of those work items.