Add a github action to auto update the gradle wrapper

[TheLimeGlass]

Description

Adds an action to automatically update the Gradle wrapper to the latest version assuming it passes successfully.

See the GitHub bot commiting the changes at my branch https://github.com/TheLimeGlass/Skript/tree/update/gradle-example
and eventually here when the schedule is triggered which is set to weekly.

Task breakdown:

1. Gets latest public Gradle release then collects the JSON result saving the version and download url
2. Applies the version to the gradle.properties
3. Runs the existing gradlew wrapper and tells it to update to the version in the gradle.properties
4. After the wrapper is updated, we run a wrapper validation to verify that the wrapper is true
5. Run a Skript quickTest
6. Commits the changes in the gradle/wrapper folder using the official GitHub actions bot if none of the tasks failed.

Gradle updated to version 13 today, so it's the best time to update.

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Target Minecraft Versions: any
Requirements: none
Related Issues: none

[Pikachu920]

I like the idea, but how likely are we to encounter breaking changes? Can we attempt to build skript and not autoupdate if it fails?

[Pikachu920]

ooh I think it does that already. awesome

can we use this too? https://github.com/marketplace/actions/verified-bot-commit