no-unused: JsxFragment requires React

Fixes: #87

Author: ajafff

rules/noUnusedRule.ts

@@ -89,7 +89,7 @@ function containsJsx(node: ts.Node): boolean | undefined {
     switch (node.kind) {
         case ts.SyntaxKind.JsxElement:
         case ts.SyntaxKind.JsxSelfClosingElement:
-        // TODO add JsxFragment
+        case ts.SyntaxKind.JsxFragment:
             return true;
         default:
             return ts.forEachChild(node, containsJsx);

test/rules/no-unused/default/jsx-fragment.tsx.lint

@@ -0,0 +1,4 @@
+import * as React from 'react';
+
+let foo = <></>;
+    ~~~ [Variable 'foo' is unused.]