Add a simple JSDuck config file

Running jsduck command generates API documentation to docs directory.

Change-Id: I1f9acbaf7868ebf48a56d20d6906cbcf23ef9748

jsduck.json

@@ -0,0 +1,6 @@
+{
+	"--title": "RevisionSlider - Documentation",
+	"--external": "jQuery,OO.ui.PanelLayout,OO.ui.Process",
+	"--output": "docs",
+	"--": "modules"
+}

modules/ext.RevisionSlider.fetchRevisions.js

@@ -2,6 +2,7 @@
 	mw.libs.revisionSlider = mw.libs.revisionSlider || {};
 
 	/**
+	 * @member RevisionSlider
 	 * Fetches up to 500 revisions at a time
 	 *
 	 * @param {Object} options - Options containing callbacks for `success` and `error` as well as fields for