Shadertoy Custom Texures

Allows custom 2D textures, music and videos to temporarily be used in Shadertoy

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