Add linting for yaml files

[ciarams87]

Proposed changes

Problem: The yaml files in the repo were not linted.

Solution: Add yamllint step to pre-commit and as a CI step. All yaml files except the helm template files will be linted before every commit (with some rules excepted for the .github workflow files, any yaml files that include raw NGINX config, and line length in the deployment yaml). Linting rules are in the .yamllint.yaml file in the root of the repo. For details on the linting rules, see: https://yamllint.readthedocs.io/en/stable/rules.html#

Testing: Verified yaml files are linted on pre-commit.

Closes #539

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

[pleshakov]

👍