contribution guidelines

CONTRIBUTING.md

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+# How to contribute
+
+Thank you for considering to contribute to this project to make it the best it can be.
+
+To make this process as frictionless as possible please read through the information in this document.
+
+First up, check existing [issues](https://github.com/MaxMaeder/DriveBackupV2/issues) and [pulls](https://github.com/MaxMaeder/DriveBackupV2/pulls), maybe it has already been submitted or someone else is already working on it, or if you want to find something to contribute to.
+
+## Non Code Contributions
+
+For contributing to translations see [translations/README.md](translations/README.md)
+
+If you found a bug or want to suggest a new feature see [issues/new/choose](https://github.com/MaxMaeder/DriveBackupV2/issues/new/choose) pick an option and fill out the relevant info
+
+## Code Contributions
+
+### Java
+
+The plugin is build using Maven, to build the plugin use `mvn package`. Build artifacts can be cleaned with `mvn clean`.
+
+We recommend [IntelliJ IDEA](https://www.jetbrains.com/idea/) as an IDE, but others like [VSCode](https://code.visualstudio.com/) or [Eclipse IDE](https://eclipseide.org/) should also work fine.
+In any case make sure you can build/run/debug from within your IDE ([steps for IntelliJ](https://gist.github.com/StillGreen-san/e2c42fee924612eb44319cf6d62d93c5)).
+
+We don't employ any automatic formatting, just keep formatting consistent with the rest of the codebase.
+See [style guide](DriveBackup/styleguide.md) for details.
+
+The [style guide](DriveBackup/styleguide.md) also includes more general advice, make sure to read it.
+
+We target Java 8 to support older versions of Minecraft and not introduce additional requirements when using them.
+
+Kotlin is not accepted into the codebase, as that would increase complexity.
+
+Each of your commits should leave the plugin in a working state.
+
+Before submitting your changes make sure to test them using the latest LTS JRE.
+If you need to test changes that affect an uploader test with a backup >= 5GB where possible.
+
+When submitting your change specify what you tested, especially if you could not test all affected components.
+