Shadertoy Custom Texures

To load an image/audio/video file, drag and drop it either from your computer or a text/web link onto one of the texture preview slots.

Note that:
1. for textures it only works for 2D types
2. loading images from the web maybe blocked due to cross-origin HTTP requests not being allowed on their servers
3.for text/web links, only ones starting with https will work due to mixed content restrictions

Version 1.4
* removed unnecessary tab permissions

Version 1.3:
* added support for audio and videos files

Version 1.2:
* custom loaded textures now use the same ID as one from shadertoy.com, so you can save projects without issue
* the "changes you made may not be saved" popup will now not be triggered when loading a custom texture over an existing texture

Version 1.1:
* the texture filter and wrap settings are now read from the correct place