added doc string

src/org/rascalmpl/interpreter/utils/IResourceLocationProvider.java

@@ -4,6 +4,14 @@
 
 import io.usethesource.vallang.ISourceLocation;
 
+/**
+ * This is a injected configuration parameter of a Rascal run-time
+ * environment like IRascalMonitor and IDEServices. The goal is
+ * to find all the file names that have the given `fileName` in
+ * the current run-time environment. For compiled Rascal this would
+ * be ClassLoader.findResources, while for the interpreter it is 
+ * typically a search through all the roots of the source folders.
+ */
 public interface IResourceLocationProvider {
     Set<ISourceLocation> findResources(String fileName);
 }