Upload plugin as part of release workflow

[Dekkonot]

This adds a script for uploading the plugin to Roblox as part of the release workflow. This is motivated by the fact that Roblox hides uploads by non-ID verified people by default, and group assets use the ID verification of whoever uploaded them. So, it's not sustainable for me to just manually upload them because I am not ID verified on Roblox.

We can get around this by just... having an ID verified user upload it every time. We needed to automate uploading the plugin anyway, so it's been moved to the release workflow. There is not a way to do this directly, as Roblox still does not have a way to upload plugins with Open Cloud. However, there is a way around it. With their Cloud Luau Execution feature, we can use AssetService:CreateAssetVersionAsync to upload the plugin in-engine.

This adds a UploadDetails.json to the root of the plugin because it's the most convenient way to pass information into Roblox. I would like these details to be configurable via variables rather than hard-coded but that technology does not exist yet (Rojo able to set values based on the environment when?). It runs whenever the release workflow is ran, and skips pre-release versions.

To use this, someone who is ID verified (cc @boatbomber) will need to make an Open Cloud API key on Roblox's website with the following characteristics:

• Both luau-execution-sessions:read and luau-execution-sessions:write (we need it to create a new task, and to read the results of the one created)
• Able to run in the Rojo-owned place on Roblox. The name of the game is Battleground because Roblox still doesn't let you configure scope by anything other than name.
• Make that token an actions secret with the name PLUGIN_UPLOAD_TOKEN