Add an FAQ section - suggestions welcomed

[hrecht]

Some of the documentation might be easier to navigate in a Frequently Asked Questions section.
Possible topics:

• Troubleshooting and getting help existing - all of this could be reformatted as FAQ
• Why can't I get ACS data for XXXX year? (Because the ACS didn't exist yet!)
• Why isn't recent PEP data in the APIs? (Because the Census Bureau didn't add it.)
• Links to info on Census geographies - tracts vs ZCTAs etc

[hrecht]

The in-progress FAQ page is now at https://www.hrecht.com/censusapi/articles/frequently-asked-questions.html with some content moved from getting started and some new.