Issue #3510730: add an api file

Closes #3510730

jstimer.api.php

+<?php
+
+/**
+ * @file
+ * Hooks provided by the Jstimer module.
+ */
+
+/**
+ * Builds the JS for a widget.
+ *
+ * @see jst_clock_jstwidget().
+ * @see jst_timer_jstwidget().
+ */
+function hook_jstwidget() {
+  // No example.
+}