challenges hint system

Hints should be uploaded to CTFd.

• Hint content can contain either plaintext, markdown and/or html
• Hint Prerequisite, hints needs to be opened in a particular order
• Sorting of hints, now sorts by cost -- fixed by https://git.cs.kau.se/csma/cyber-range/ctfd-plugins/-/issues/2
• Negative points of hints -- fixed by https://git.cs.kau.se/csma/cyber-range/ctfd-plugins/-/issues/2