Summary:
Added eslint config and added lint.sh files.
Fixed all existing lint issues.
This is in preperation for moving docs outside of our repo so that we have external
contributors to it.

Test Plan: Run `./lint.sh`

Reviewers: michelle, malthus, #engineering

Reviewed By: michelle, #engineering

Differential Revision: https://phab.corp.pixielabs.ai/D3467

GitOrigin-RevId: 6b2a2564591e56985c3c62088adc366a4b8cc6f0