* update appimage build
* update Qt version in BUILD.md
* add AppImage to CI build
* add statically linked package for Ubuntu 20.04
* add statically linked deb to CI build
* add XDG MIME support
* force XDG icon spec
With the addition of MIME support, it is no longer possible to integrate with desktop environment by simply moving desktop file to standard location. Now force XDG_ADAPTIVE_ICON=ON.
If you build Red Panda C++ with non-standard PREFIX, you will move all desktop integration components to standard location.
* fix linux build error
* Linux packaging: remove Alacritty from AppImage
* limit APP_DIR trick to Windows only
* implement Windows search path
* fix terminal search
* Arch Linux packaging; make LIBEXECDIR configurable
* update docs
* resolve libexec and share from relative path
* AppImage packaging
* allow build AppImage on Windows host