feat: Add announcements

[madkarmaa]

What's this?

This is a new, more updated continuation of #195

TODO:

• Footer shifts up when content is little Out of scope of this PR
• When inside an announcement (/announcement/X) make clicking on the nav tab "Announcement" go back
• Handle nullable properties of announcement object
• Settings dialog needs to be redesigned (Move login dialog stuff into the settings dialog) This is too big of a feat for this due to spaghetti code, it should be part of the major rewrite
• Action buttons in announcement for admins need to be img wrapped in buttons
• Removing tags in announcement when editing it should be done by simply clicking on the tag
• Adding attachments should behave the same as adding tags
• If attachment URLs are empty, prevent saving the announcement edit
• In edit announcement fields null can not be expressed (For example the author field left empty saves an empty string in API)
• Attachment textbox string overflows into bin icon
• In mobile view the separators should be full width
• Title is not nullable, but an announcement can still be created with an empty title
• If a date is near the current one, it should be displayed in relative time (For example when the announcement was just created
• Text should not be red in the "Expired login" dialog
• Switch date in footer with content in header
• Inspecting the network tab, query is making fetches every couple of seconds for individual announcements for no reason
• Enter button to submit login in login dialog doesn't work
• Creating a new announcement/updating it does not update it in the "announcements" page unless you refresh the page (Cache problem?)
• The plus icon in the create announcement button is not dark