Replace jasmine+karma with jest

Hi Hackers,

I suggest we should replace jasmine+karma combination with jest for the following reasons:

1. Jest is a zero dependency, less config testing framework.

2. Has built in support for React. Easy to write React test cases. Jasmine is more for Angular than React.

3. Jasmine requires enzyme to be installed separately, which is not always up to date with latest React versions. https://github.com/enzymejs/enzyme/issues/2524 it still doesn't support React 18.

3. Used by Facebook for React testing.

4. In built code coverage.

5. Allows React component mocking which is not possible with jasmine yet.

6. It is jasmine compatible, so easy to migrate.

7. Future proof.

What do you think?