Setup React component testing

[BenediktSeidlSWM]

This pull request contains some basic setup for testing React components using the "React Testing Library" [1] and Jest. Note that the babel config file needs to be renamed in order for babel to consider the node_modules folder. [2]

Before writing more tests in this style, I would like to hear from you if this kind of testing is desirable for the qwc2 project. Thanks!

[manisandro]

Thanks for your work on this! I'd say this is definitely desirable.

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[BenediktSeidlSWM]

It seems like I broke ci by renaming eslint.yml to ci.yml. Would you prefer separate jobs for linting and testing? Also, please note that I introduced SARIF_ESLINT_IGNORE_SUPPRESSED so that eslint errors that are disabled inline no longer show up on GitHub.

[manisandro]

Maybe it's easier to keep them separate? SARIF_ESLINT_IGNORE_SUPPRESSED looks good to me.