Add string to Tether.ITetherOptions.classes (#26873)

Boolean is used for disabling classes while strings is used for overriding. See docs: http://tether.io/

types/tether/index.d.ts

@@ -24,7 +24,7 @@ declare namespace Tether {
     interface ITetherOptions {
         attachment: string;
         bodyElement?: HTMLElement;
-        classes?: {[className: string]: boolean};
+        classes?: {[className: string]: boolean | string};
         classPrefix?: string;
         constraints?: ITetherConstraint[];
         element?: HTMLElement | string | any /* JQuery */;

types/tether/tether-tests.ts

@@ -9,7 +9,11 @@ new Tether({
     targetAttachment: "top middle",
     targetModifier: "visible",
     offset: "-15px 0",
-    targetOffset: "0 0"
+    targetOffset: "0 0",
+    classes: {
+      'element': false,
+      'target': 'someClassName'
+    }
 });
 
 new Tether({
@@ -50,4 +54,3 @@ new Tether({
         }
     ]
 });
-