JS: Add ImportSpecifier.getImportDeclaration()

Author: asgerf

javascript/ql/lib/semmle/javascript/ES2015Modules.qll

@@ -174,6 +174,9 @@ private class LiteralImportPath extends PathExpr, ConstantString {
  * ```
  */
 class ImportSpecifier extends Expr, @import_specifier {
+  /** Gets the import declaration in which this specifier appears. */
+  ImportDeclaration getImportDeclaration() { result.getASpecifier() = this }
+
   /** Gets the imported symbol; undefined for default and namespace import specifiers. */
   Identifier getImported() { result = this.getChildExpr(0) }