feat(Asset): Add asset sharing

[Kruptein]

This PR adds the capability to share assets with other users on the same server. Either singular files or entire folders can be shared.

These are shared in either a "view only" or an "edit" mode. In the latter mode users can fully modify the contents of a folder including addition as well as removal of assets, so be warry with this right.

In view mode, the only thing the user can do is see the contents of the folder and drop the assets in their campaigns.

When a campaign is shared it appears in the root folder of the receiving user in the form of ${ownerName}-${assetName} with a special icon signifying it was shared with you. You're free to rename and move this asset around and it won't affect anything for the original user. This is purely an anchor to link into the real asset when you enter it.

A warning banner is shown when you're browsing the content of a shared folder, indicating that if you do have edit rights, you need to be extra careful.

To configure the sharing itself, a new entry has been added to the right click context menu in the asset manager.

This closes #1298

[Kruptein]

Core logic is mostly done, the main two things remaining to do are:

• [x] Update in-game assets sidebar to include shared assets
• [x] Properly make the share modal UI