Turned level 3 into unfinished level

[WimYedema]

Also changed health status bar to hearts and reduced health to 5. The baddies no longer hurt when they hit during hurting.

===:clipboard: PR Checklist :clipboard:===

• 📌 issue exists in github for these changes
• 🔬 existing tests still pass
• 🙈 code conforms to the style guide
• 📐 new tests written and passing / old tests updated with new scenario(s)
• 📄 changelog entry added (or not needed)

==================
Closes #41

Changes:

• Turned health status into 5 hearts, also reducing health from 100 to 5
• Repeated hits from a baddie no longer hurt when the player is still hurting
• Turned level 3 into a somwhat interesting, but unfinished, level
• Removed the ability to jump during a fall