fix(seed): Add test for checking the length of buttons is 2

seed/challenges/03-front-end-libraries/bootstrap.json

@@ -392,7 +392,7 @@
         "</div>"
       ],
       "tests": [
-        "assert(new RegExp(\"like\",\"gi\").test($(\"button\").text()), 'message: Create a new <code>button</code> element with the text \"Like\".');",
+        "assert(new RegExp(\"like\",\"gi\").test($(\"button\").text()) && ($(\"img.img-responsive + button.btn\").length > 0), 'message: Create a new <code>button</code> element with the text \"Like\".');",
         "assert($(\"button\").hasClass(\"btn\"), 'message: Your new button should have the class <code>btn</code>.');",
         "assert(code.match(/<\\/button>/g) && code.match(/<button/g) && code.match(/<\\/button>/g).length === code.match(/<button/g).length, 'message: Make sure all your <code>button</code> elements have a closing tag.');"
       ],