public-sans.digital.gov accessibility testing

[jAigret-Bix]

Task on uswds/uswds-team#7
In FY 2020, based on the Modernization Plan for public-sans.digital.gov🔒, we will make the following improvements on https://public-sans.digital.gov:

• Incorporate a11y testing (est. 10-20 hours)

• Test key pages (home and specimen). Begin w lighthouse and move to accessibility insight. Good selection of representative pages.

[mejiaj]

@thisisdano should we be using master or develop? They seem to be very different.

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Created a test branch called jm-a11y-testing based off of master. It removes some packages, updates nvmrc, and adds a local accessibility test.

✅ No a11y issues found on home/specimen page.

[mejiaj]

PR submitted

uswds/public-sans#179

[thisisdano]

OK, all done.