Add basic groovy code style validation.

IDK how well this would work on a gradle script but might be interesting to try on yarn or something.

build.gradle

@@ -7,6 +7,7 @@ plugins {
 	id 'groovy'
 	id 'checkstyle'
 	id 'jacoco'
+	id 'codenarc'
 	id "org.cadixdev.licenser" version "0.5.0"
 }
 
@@ -110,6 +111,11 @@ checkstyle {
 	toolVersion = '8.39'
 }
 
+codenarc {
+	toolVersion = "2.0.0"
+	configFile = file("codenarc.groovy")
+}
+
 gradlePlugin {
 	plugins {
 		fabricLoom {