[FEATURE] Fix Asset base class inheritance

This fixes the broken inheritance for the Asset class.

Related: #47428
Related: #47262
Related: #45003
[TASK] Add constructor to Asset class

This moves the constructor from Image to Asset to ease inheritance.

Related: #47428
Related: #45003
[FEATURE] Add Document and Video assets

Related: #45003
[TASK] Remove version and add license to composer manifest

Change-Id: I2b5dc852919945e92de66cafbe762202f639db65
Related: #45003
[TASK] Tweak README.md

Change-Id: I225fd77217ae79a18afd5978ecf80e6c2d5345a8
Related: #45003
[TASK] Adjust package resources structure

This adjusts the resources structure to follow the convention of
Scripts, Styles, Libraries.

Change-Id: I8e267b23500c861295f491735d20e24d47a6d991
Related: #45003
[FEATURE] Add Audio asset type

Change-Id: I6f61486bc926f143d729f6bc3939025f20e80476
Related: #45003
[FEATURE] Asset admin UI

Change-Id: Ic4ec1e85708ba02437bb95b885d458fb010fbd57
Related: #45003
[FEATURE] Add Tags for Assets

This provides basic tagging for assets.

Change-Id: I31cfd84f5c1a874fe3699f5b59431fd03bef4360
Related: #45003
[FEATURE] Upload assets using drag and drop

In the asset list view assets can be uploaded by dragging them to a
upload drop zone.

Change-Id: Idcf39aace12a2217e495b8a3c814ecd314932a1f
Related: #45003
[TASK] Merge branch 'dev'

Change-Id: I0d12fe3381a0809e0a919a17a6fd93e952d70c04
Related: #45003