Add Flutter Courses

[ishandeveloper]

Follow the guidelines in 'How To Contribute' section of README.md

and add a course that you've taken before or would like to recommend to others, related to flutter.

[ashandilya]

Can I contribute into this??

[ishandeveloper]

Sure @ashandilya . There's no need to assign the issue, go ahead and make a PR. Goodluck ! ✨