Add dependency checking

[mak448a]

Use x-checker-data

[mak448a]

This should allow me to close https://github.com/mak448a/Qtcord/issues/75 and stop having to manually update dependencies. Maybe I should even add

"x-checker-data": {
    "type": "rotating-url",
    "url": "http://example.com/last-version",
    "pattern": "http://example.com/foo-v([0-9.]+).tar.gz"
}

from here to auto update the app too.

[flathubbot]

Started test build 158879

[flathubbot]

Build 158879 failed

[mak448a]

bot, build io.github.mak448a.Qtcord

[flathubbot]

Queued test build for io.github.mak448a.Qtcord.

[mak448a]

bot, cancel build

[flathubbot]

I'm sorry, i did not understand that command.

[flathubbot]

Started test build 158890

[flathubbot]

Build 158890 failed

[flathubbot]

Started test build 158907

[flathubbot]

Build 158907 failed

[mak448a]

bot, build

[flathubbot]

Queued test build for io.github.mak448a.QTCord.

[flathubbot]

Started test build 159109

[flathubbot]

Build 159109 successful To test this build, install it from the testing repository:

flatpak install --user https://dl.flathub.org/build-repo/142192/io.github.mak448a.QTCord.flatpakref