Add annotation processors to Java build.gradle (#610)

Relies on wpilibsuite/GradleRIO#744

src/main/resources/export/java/build.gradle

@@ -58,6 +58,7 @@ wpi.java.debugJni = false
 // Defining my dependencies. In this case, WPILib (+ friends), and vendor libraries.
 // Also defines JUnit 5.
 dependencies {
+ annotationProcessor wpi.java.deps.wpilibAnnotations()
  implementation wpi.java.deps.wpilib()
  implementation wpi.java.vendor.java()