Add automated build dispatch

[dragonhunt02]

V-Sekai/v-sekai-game#482
Send automated build message to v-sekai-game on world-godot commit.

To enable it, add REPO_DISPATCH to repository secrets. It should be a generated Github Classic Token with all repo permissions enabled.

Edited:

A fine-grained token with Contents: Read and write permission on v-sekai-game repo should be placed in the REPO_DISPATCH named repository secret of V-Sekai/world-godot.

[fire]

What does this do?

[dragonhunt02]

This sends a workflow dispatch message to target repo.
When it is sent, it runs a workflow in another repo. So when world-godot is updated, message is sent to v-sekai-game repo and v-sekai-game will export binaries with the updated editor and create a nightly release.

Right now this PR lacks a step in world-godot build.yaml, I'll add it later

[dragonhunt02]

Also, you can manually send workflow dispatch messages to v-sekai-game from your command line with curl or gh

[dragonhunt02]

PR is ready

[fire]

Github Classic Token with all repo permissions enabled.

Can I reduce the permissions used?

[dragonhunt02]

I had some issues using fine grained tokens...I can run some more tests to check it again

[dragonhunt02]

A fine grained token with Contents: Read and write permission on v-sekai-game repo should work

[fire]

Done. Thanks

[fire]

I hope the merge run succeeds!