Docker Image Names need to be all lowercase

[RowMax03]

.github/workflows/build-docker-image.yml
Dosen't work if your Github Name or repository has capital letters in it.

To solve:
Just add a step to sanitize the slug of the tag before building and pushing
Explained in here:
https://github.com/razorpay/docker-build-push-action/blob/master/TROUBLESHOOTING.md

[shyim]

Do you want to open a PR?