Alpha v0.19.4

This update contains a few bug fixes, a few new features, and a bunch of improvements specifically for macOS.

Changes

• Add position to Blend Images node (#2087 -- thanks @adegerard)
• Made some node outputs more consistent (#2111 -- thanks @stonerl)
• Add "Separate Alpha" checkbox to upscale nodes (#2127)
• Handle unsaved changes on chaiNNer restart (#2132 -- thanks @stonerl)
• Various macOS DMG improvements (#2122 -- thanks @stonerl)
• Set minimum macOS version to 11.0.0 (#2124 -- thanks @stonerl)
• Remove the macOS portable build as it was broken and has likely never worked (#2119 -- thanks @stonerl)
• Associate .chn files with chaiNNer on macOS (#2115 -- thanks @stonerl)
• Add "New Chain" and "Open Recent" menus to macOS dock (#2140 -- thanks @stonerl)
• Slight optimization for NCNN model loading when using CPU NCNN (#2142 -- thanks @JeremyRand)

Bug Fixes

• Fixed bug related to opening certain older chain files (#2116)
• Fixed tooltips being placed behind modal popups (#2128 -- thanks @stonerl)
• Fixed hotkeys (such as pressing F5 to run a chain) sometimes not working (#2114 -- thanks @stonerl)
• Fixed incorrect inputs on new unified Crop node (#2134 -- thanks @adegerard)

And thanks to the following maintainers: @joeyballentine @RunDevelopment