Update dependencies and clean up the repository

[surilindur]

This is a set of changes that are all kind of connected to each other, and since only 19 files are changed, I decided to keep them in the same PR. The main changes are:

• Bumping dependencies where appropriate, and also fixing the resulting errors from version updates.
• Removing redundant files such as .DS_Store and debug that are not needed for anything and were likely included by accident.
• Moving index.ts under lib/ to ensure all the exported stuff is now under lib/ and not at the root. This also helps simplify some rules.
• Splitting Jest configs to their own file, as in the Comunica repository.
• Adding --maxWorkers=50% to the test script, because it runs a lot faster that way and uses a lot less memory. I think Jest, by default, uses way too many workers for the tests in this repository. It was eating up around 20GB of memory for me when running the tests without that worker limit, and the tests took several times longer, as well.

Any feedback would be welcome! 🙂 I just ended up having a look at this repo after some warnings appeared in Comunica link traversal (that were unrelated, I think, in the end).

[rubensworks]

Probably depends on #135.

@surilindur Can you rebase this one once #135 is merged?

[surilindur]

@rubensworks This should now be ready for review!

[rubensworks]

Thx!