Add descriptive links to other endpoint pages

[nmdefries]

Add

• [x] this link to the google survey page
• [x] these two (Social Distancing Metrics (https://docs.safegraph.com/docs/social-distancing-metrics); Weekly Patterns (https://docs.safegraph.com/docs/weekly-patterns)) to the Safegraph page
• [x] this link to the google symptoms page
• [x] links to or lists of county and region (Taipei, Northern, Central, etc) options + "Nationwide" on the nidss pages. Dengue has counties and regions and nationwide; flu doesn't have counties
• [x] Turn these links into actual clickable hyperlinks
• [x] add this link and this link to the GFT doc page.
• [x] add this link to the GHT page. there are various research papers talking about using GHT for health tracking. maybe we can add links to some of those to provide more background about the source

[nmdefries]

• [x] add license info for Taiwanese datasets

[nmdefries]

• [x] in “COVID-19 Reported Patient Impact and Hospital Capacity by State Timeseries”, the URL example is woefully out of date, e.g. it doesn’t show the fields with age breakdown. Re-executing the same URL returns an updated list, that should be put into the example in the documentation.

[tinatownes]

Addressed with pull request #1552