Alpha v0.20.2

Hey everyone, sorry it took so long to get this out. This update contains a bunch of things that I thought we had already released -- a couple bug fixes and some cool new features. Some very big things are on the way though, so be on the lookout for the next update.

Changes

• Add Multi Gaussian filter to Normal Map Generator (#2255)
• Add ability to limit the length of certain iterators (#2218)
• Add support for sub-pixel distance transform (#2235)
• (ncnn) Allow disabling Winograd/SGEMM (for cpu ncnn) (#2237 -- thanks @JeremyRand)

Bug Fixes

• Fixed being able to close the dependency manager while installing deps (#2227)
• Fixed RGBA preview image background (#2225)
• Fixed pip using bad caches on dep installs (#2232)
• Fixed dragging bug on image previews (#2236)
• Fixed bug from read-only image in CAS (#2239)
• Fixed CAS for grayscale images (#2241)

And thanks to these maintainers: @joeyballentine and @RunDevelopment