Add sunshine

[ReenigneArcher]

Adds AppImage of Sunshine

[probonopd]

Please don't do this:

https://github.com/SunshineStream/Sunshine/blob/4b658cd86ba0b7520f6f7cb5b5f07d6775845a81/.github/workflows/CI.yml#L117-L124

Instead, please add the files to the AppImage and copy them out of the AppImage when the application runs for the first time.

[ReenigneArcher]

This is ready for review now. Thanks!

[ReenigneArcher]

P.S. this image is compiled on Ubuntu 20.04 and according to appimagelint, will not run on 18.04.

The image can be compiled on 18.04, but AppImage lint fails on 18.04 (due to an issue with the tar package included in the GitHub runner).

See this unresolved issue: TheAssassin/appimagelint#28
As well as latest attempt here: https://github.com/LizardByte/Sunshine/actions/runs/3371164942/jobs/5593023238#step:8:756

GitHub is removing 18.04 runners in exactly one month though, so it will be very difficult for us to build on 18.04 even if we fix the issue with tar. https://github.blog/changelog/2022-08-09-github-actions-the-ubuntu-18-04-actions-runner-image-is-being-deprecated-and-will-be-removed-by-12-1-22/

[probonopd]

Thank you very much @ReenigneArcher