Add a script that builds an AppImage
We already have https://github.com/nuttyartist/notes/blob/dev/packaging/linux/make_deb.sh and https://github.com/nuttyartist/notes/blob/dev/packaging/linux/make_snap.sh, we should also have a script that creates an appimage.
We used to have this already, but since we switched from qmake to CMake, we lost this functionality. A good place to start would be to look at how we did it previously: https://github.com/nuttyartist/notes/blob/7f71dae920248a6b517e643d160d8a90656da675/src/Notes.pro#L164-L182
We also need to update the make_snap and make_deb scripts to account for the new CMake way of building.
We should probably switch to a different AppImage packaging tool than the one that was being used, though.
Besides not supporting Qt 6, the previous tool was just way too strict, and by design will only allow the AppImage to be created on the oldest, yet still supported, LTS release of Ubuntu, and there's no easy way to override that.
I understand it's probably for a good cause, but in my opinion, it's ultimately a design decision that shouldn't be forced upon us.
These are the new tools I'd recommend:
- linuxdeploy: https://github.com/linuxdeploy/linuxdeploy/
- linuxeploy's Qt plugin: https://github.com/linuxdeploy/linuxdeploy-plugin-qt/
We could even just adapt from what the CI does:
https://github.com/nuttyartist/notes/blob/dfd0756815a43f3831cb594d1bc52f24e2229a3b/.github/workflows/linux.yml#L195-L223