Feat/settings page

[JulianDietzel]

Closes #326. Check the issue for a comprehensive list of all the changes made. The short version is:

• A settings page with options for video embed preferences was added
• A component, which allows the user to allow video embeds was added and is shown instead of a video if the permission has not been granted
• A very small system was added to store the user preferences in the local storage of the users browser