feat: enable video content

[kaljarv]

WHY:

Fixes #387

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

• Adds a <Video> component that can be used to display video
• Adds a video slot to the <BasicPage> template
• Adds a sanitizeHtml utility for cleaning up user-supplied HTML content
• Enables automatic switching between video and normal views for questions, if they contain video properties in the customData

Check off each of the following tasks as they are completed

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

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