Make the panning match the cursor
Enforce a minimum zoom that will keep the edges of the sphere from showing
	This probably just needs simple math with the aspect and/or the viewport's diagonal length.
Enforce a maximum zoom that matches the pixel density of the original image at its natural dimensions, normal to the camera
Choose a pleasant initial zoom
Allow pinch-zooming
Add data- attribute for minimum zoom
Add data- attribute for starting angle
Add data- attributes for canvas dimensions
Automatically create canvas for each marked <img> once it loads, and display:none the <img>
Set default canvas dimensions to match the size of the image
Add a class to the <canvas> for styling
Copy matrix funcs into code
Add licenses
Add instructions
Fix up code locality
Give the uniforms simpler names
Allow setting top and bottom angles in case the photo doesn't reach to the poles
