feat: Zoom and Drag

[neptuwunium]

includes #3 and #4

Adds:

• "Auto" label for height when it is Zero
• Several fixes for Pow2Spinbox for height specifically
• Fix scrolling Pow2Spinbox re-rendering the image several times due to 0 step increments
• Scroll zooming for the image
• Drag moving for the image
• Double click to reset position and scale

PR 4 Adds:

• Modifies the title to show the loaded file path
• Adds ASTC support
• Adds ETC support
• Significantly refactors BPTC code to support ASTC's varying block sizes
• Bumps BCDec to my fork which as slightly more accurate BC3 and BC4 decoding (relative to modern GPUs, less accurate compared to older GPUs due to the math changing several times over time)

PR 3 Adds:

• a height spinbox that will default to the old behavior when it is zero.
• the image to be in the horizontal and vertical center of the viewer.

[Puxtril]

A wonderful PR, thanks a bunch!

The zoom/scroll is very helpful for all use cases. I've never come across the other compression formats myself, but I'm sure they'll prove useful to those who need it.