Migrate tests from Mocha to Jest

[Pringels]

We want to use Jest and react-testing-library to test the 3.0 version. Migrate all the existing tests to Jest syntax, and make any required adjustments to the mocks/specs if required.

[theashraf]

I'd like to help with this one

[Pringels]

@theashraf sure thing! you can check out https://github.com/jerairrest/react-chartjs-2/tree/feature/chartjs3-rewrite and start there. The Jest setup is already up and running. you'll have to copy the tests from what is currently on master.

If you experience any issues with Typescript let me know. I hastily added some types but I suspect it's not quite 100% yet.