Development: Implement PR checks for frontend

[natalialuzuriaga]

BRIEF DESCRIPTION

Implement PR checks for frontend, take a look at this: https://github.com/18F/guides/blob/main/docs/development.md

Currently, we have code linting and styling using eslint and prettier. We should implement checks for automated accessibility testing, HTML vaildation, and internal linking:

SKILLS NEEDED

Frontend, Web Dev

[natalialuzuriaga]

Related to #274