HMM Problem Pull Request (wait with merge)

[Sungonogi]

Haven't really started with the HMM problem yet, but already opened a PR to work on.

I already

• added some setup information to the README
• added animation when clicking "check" to make it clear that clicking "check" actually does something even when response stays the same (before that it was a bit unclear if the changed answer was actually checked again, when the error message stayed the same)
• added setTimeout so the text "generating problems" is actually rendered, especially important for "new problems" button