Migrate from GitLab CI to GitHub Actions

[neelkamath]

1. Create a GitHub Actions workflow based on .gitlab-ci.yml. Name the workflow .github/workflows/workflow.yml. The workflow should run on pushes to the master branch, and on pull requests. Here's an example snippet:

   on:
     push:
       branches: [ master ]
     pull_request:

2. Delete the GitLab CI file.

If you'd like to work on this, leave a comment saying something like "I'll work on this.", and you can begin without waiting for me to OK it. The point of writing the comment is to let others know that this issue has already been taken up.

[garg-saurav]

I'll work on this

[garg-saurav]

Looks like there is some issue in the yml file. Others can pitch in.

[geekypandey]

@garg-saurav Hey hi, are you still working on this issue?

[geekypandey]

@neelkamath Can I take up this issue if @garg-saurav is not currently working on it?

[neelkamath]

@geekypandey Yes, please.