Prompt user when exiting from the edit page if some of the fields have been changed

[Shiroizu]

Is your feature request related to a problem? Please describe. (required)

Sometimes users accidentally exit the entry edit page, making their changes disappear.

Describe the solution you'd like. (required)

Implement a prompt using beforeunload-event or something similar to prevent accidental edit page exits when some of the fields have been changed.

Relevant discussion here: https://vocadb.net/S/634358

Describe alternatives you've considered. (optional)

How should the UI look like? (illustrate it) (optional)

Additional context (optional)

Checklist (required)

Fill out the checklist.

• Searched VocaDB/vocadb for duplicate issues.