feat: prompt user - unsaved changes & nav away

[xgui3783]

• Run npm test successfully.

• Run npm run mochasuccessfully.

• test_screenshots generates the same test pictures in test as there were in test/reference and does not show any errors

(I don't think new screenshots are generated properly?)

• I implemented tests for the new changes OR

• These changes do not require tests because _____

• These changes fix Alert user before closing without saving #36

[xgui3783]

Unfortunately, I can't seem to test this functionality properly. The bundled images seems to have Hash to be undefined.

I will have to take a better look when I get a chance.

[katjaq]

Thank you so much for implementing this alert! 🌟
Could you check if the Hash is really used somewhere? It is maybe implemented in the client but not in the server?