adding validate github action to pull requests raised to the master branch

[gligorkot]

What did you implement:

Addresses a part of #645

How did you implement it:

Added a validate Github action to lint and run unit tests + report coverage

How can we verify it:

It should run on Github when a PR is raised to the master branch

Todos:

Note: Run npm run test:ci to run all validation checks on proposed changes

• Ensure there are no lint errors.
  Validate via npm run lint
  Note: Some reported issues can be automatically fixed by running npm run lint:fix
• Write tests and confirm existing functionality is not broken.
  Validate via npm test
• Write documentation
• [ x Provide verification config / commands / resources
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: YES
Is it a breaking change?: NO

[gligorkot]

@medikoo this adds the validate.yml asked for in #645 - trying to get us closer to a release. Can you please have a look if this is what you expected?

[medikoo]

Looks great. Thank you @gligorkot !