add discourse-details plugin

plugins/discourse-details/assets/javascripts/details.js

@@ -0,0 +1,58 @@
+(function(document, $) {
+
+  // cf. http://mths.be/details
+  var hasNativeSupport = (function(doc) {
+    var fake, el = doc.createElement("details");
+    // fail-fast
+    if (!("open" in el)) { return false; }
+    // figure out a root node
+    var root = doc.body || (function() {
+      var de = doc.documentElement;
+      fake = true;
+      return de.insertBefore(doc.createElement("body"), de.firstElementChild || de.firstChild);
+    })();
+    // setup test element
+    el.innerHTML = "<summary>a</summary>b";
+    el.style.display = "block";
+    // add test element to the root node
+    root.appendChild(el);
+    // can we open it?
+    var diff = el.offsetHeight;
+    el.open = true;
+    diff = diff !== el.offsetHeight;
+    // cleanup
+    root.removeChild(el);
+    if (fake) { root.parentNode.removeChild(root); }
+    // return the result
+    return diff;
+  })(document);
+
+  function toggleOpen($details) {
+    $details.toggleClass("open");
+  }
+
+  $.fn.details = function() {
+    if (hasNativeSupport) { return this; }
+
+    return this.each(function() {
+      var $details = $(this),
+          $firstSummary = $("summary", $details).first();
+
+      $firstSummary.prop("tabIndex", 0);
+
+      $firstSummary.on("keydown", function(event) {
+        if (event.keyCode === 32 /* SPACE */ || event.keyCode === 13 /* ENTER */) {
+          toggleOpen($details);
+          return false;
+        }
+      });
+
+      $firstSummary.on("click", function() {
+        $firstSummary.focus();
+        toggleOpen($details);
+      });
+
+    });
+  };
+
+})(document, jQuery);