JavaScript: Add missing qldoc.

javascript/ql/src/semmle/javascript/Files.qll

@@ -199,6 +199,11 @@ class Folder extends Container, @folder {
 
 /** A file. */
 class File extends Container, @file {
+  /**
+   * Gets the location of this file.
+   *
+   * Note that files have special locations starting and ending at line zero, column zero.
+   */
   Location getLocation() { hasLocation(this, result) }
 
   override string getAbsolutePath() { files(this, result, _, _, _) }

javascript/ql/src/semmle/javascript/JSDoc.qll

@@ -74,6 +74,7 @@ abstract class Documentable extends ASTNode {
 class JSDocTypeExprParent extends @jsdoc_type_expr_parent, Locatable {
   override Location getLocation() { hasLocation(this, result) }
 
+  /** Gets the JSDoc comment to which this element belongs. */
   JSDoc getJSDocComment() { none() }
 }