Spotless formatter

[jennatripoli]

Added Spotless code formatter to build.gradle to enable the Gradle command spotlessApply to apply formatting rules to all files. Specifically, these rules follow the Google Java Style Guide.

I opted to not apply the changes here since (for now) I do not think we need to apply the formatting to this repository. I created a branch (Jenna-SpotlessFormatterApply) where I ran the formatter so the changes can be viewed there. The main violations included the line length and blank lines.

The spotlessCheck command was modified from its out-of-the-box version to warn rather than error when there are formatting violations. This is in an effort to not create barriers to the development workflow, especially during high-impact times like competition.

When the check fails, the following message appears in the console:

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Spotless found formatting violations in Java!

1. Open the WPILib Command Palette
2. Select WPILib: Run a command with Gradle

Run spotlessCheck to see the violations
Run spotlessApply to automatically fix violations
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[jennatripoli]

google-java-format fails when imports are not continuous, which in this case is caused by the commented lines