Use groovy support when editing Gradle files

The Gradle build tool provides two DSLs for configuring builds. On is
based on Groovy and Gradle build files written in Gradle Groovy DSL use
*.gradle file ending.

This change adds `gradle` to the supported file types of the groovy
language configuration.

languages.toml

@@ -3130,7 +3130,7 @@ source = { git = "https://github.com/apple/tree-sitter-pkl", rev = "c03f04a313b7
 name = "groovy"
 language-id = "groovy"
 scope = "source.groovy"
-file-types = ["groovy", "jenkinsfile", { glob = "Jenkinsfile" },  { glob = "Jenkinsfile.*" }]
+file-types = ["gradle", "groovy", "jenkinsfile", { glob = "Jenkinsfile" },  { glob = "Jenkinsfile.*" }]
 shebangs = ["groovy"]
 comment-token = "//"
 indent = { tab-width = 2, unit = "  " }