Support building AppImage installer [2 XMR]

[woodser]

This issue requests building an AppImage installer from the Haveno repo.

The AppImage should be built as part of the existing installer build process with ./gradlew packageInstallers. See package.gradle within ./desktop to add support for building AppImage.

This script is invoked as part of GitHub Actions, in order to automatically create the installers, which users can verify against installers posted for download.

Here are related instructions to manually build the installers, if useful.

Related: #862 (comment), #270 (comment)

[github-actions]

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[niyid]

I'm on it...

[woodser]

Thanks very much for your help @TheTollingBell. Please feel free to provide a payment address address here or DM.

[TheTollingBell]

I deleted the Monero chain off my computer so you might have to wait a day for the sync.

[woodser]

No problem :)

Confirming my matrix account.

[TheTollingBell]

Confirming my matrix as well. Syncing should be done in 6-8 hrs hopefully.

[TheTollingBell]

@woodser Ready to recieve at:

45ZXas7gQJmUKHqJsxbP2mgupHRGcSRe5Z42QDcAXTFi3meXmGm7AaUSGhid8ZXb1m1Q74EZeHUBqVe4hSFD9vNsEt4fzdz

[woodser]

Payment sent. Thanks!