Add tests for archetype-plugin compilability

This should make sure that the example plugin archetype is compilable.
The test seems to fail in IDEA, but runs fine from a terminal :/

runelite-plugin-archetype/src/test/resources/projects/compilationtest/archetype.properties

@@ -0,0 +1,5 @@
+sourceEncoding=UTF-8
+groupId=org.example.runelite
+artifactId=exampleplugin
+version=1.0.0-SNAPSHOT
+package=org.example.runelite.exampleplugin

runelite-plugin-archetype/src/test/resources/projects/compilationtest/goal.txt

@@ -0,0 +1 @@
+clean verify