feat: don't allow modification if answers are locked and display a notification (#210)

[eemelioksanen]

WHY:

Implements the rest of the features in #210.

What has been changed (if possible, add screenshots, gifs, etc. )

Check off each of the following tasks as they are completed

• [ ] I have reviewed the changes myself in this PR. Please check the self-review document
• [ ] I have added or edited unit tests.
• [ ] I have run the unit tests successfully.
• [ ] I have run the e2e tests successfully.
• [ ] I have tested this change on my own device.
• [ ] I have tested this change on other devices (Using Browserstack is recommended).
• [ ] I have tested my changes using the WAVE extension
• [ ] I have added documentation where necessary.
• [ ] Is there an existing issue linked to this PR?

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