Resources Page

Created by: bretthayes

This closes #5651 and adds a new Resources page.

Changelog

• Added "All Resources" nav item to the top nav
• Added static data, Filters, Card, and template index for the Resources page
• Updated our RequestDemoTrySourcegraph CTA with two variants from our DLS
• Fixed a bug I noticed where markup was invalid for our CastStudyCard component

Test

1. Ensure prettier has standardized the proposed changes.
2. Ensure all links are ok for each card in the resources page
3. Ensure filters work properly for content types and subjects

---

• To see the specific tasks where the Asana app for GitHub is being used, see below:
  • https://app.asana.com/0/0/1202769406180424