feat(actions): add github action to validate and diff pull request

[hiteshnayak305]

Description of the change

Support for validation on a pull request.

On pull request

• helm lint is run
• helm template is run with default pvc test-pvc to detect any compilation error

• int128/diff-action@v1 (compare final manifest with main branch) Will only run on pull request to main and feature/pr-action branches

  1. If there is no any change in final manifest then there will be no comment. (limitation: no action on empty diff in dependency action library)

  2. If there is some change in final manifest a bot will put a comment with diff in final manifest. Pull Request Example

Applicable issues

• fixes #81

[hiteshnayak305]

accepting command in comments is little tricky, please let me know if any suggestions