Include shasums in releases

[pepicrft]

For security, it'd be useful to include the shashums of the release artifacts so clients can check if they match after having downloaded the artifacts. There are GitHub actions like this one that ease calculating them and uploading the values to the GitHub release.

[f-trycua]

These are now added to each release e.g. https://github.com/trycua/computer/releases/tag/lume-v0.1.17

[pepicrft]

Thanks @f-trycua