Add support for new @supports at-rule.

Author: philipwalton

index.js

@@ -175,6 +175,25 @@ module.exports = function(css){
     };
   }
 
+  /**
+   * Parse supports.
+   */
+
+  function supports() {
+    var m = match(/^@supports *([^{]+)/);
+    if (!m) return;
+    var supports = m[1].trim();
+
+    if (!open()) return;
+    comments();
+
+    var style = rules();
+
+    if (!close()) return;
+
+    return { supports: supports, rules: style };
+  }
+
   /**
    * Parse media.
    */
@@ -250,6 +269,7 @@ module.exports = function(css){
   function atrule() {
     return keyframes()
       || media()
+      || supports()
       || atimport()
       || atcharset();
   }

test/cases/supports.css

@@ -0,0 +1,6 @@
+@supports (display: flex) or (display: box) {
+  .flex {
+    display: box;
+    display: flex;
+  }
+}

test/cases/supports.json

@@ -0,0 +1,26 @@
+{
+  "stylesheet": {
+    "rules": [
+      {
+        "supports": "(display: flex) or (display: box)",
+        "rules": [
+          {
+            "selectors": [
+              ".flex"
+            ],
+            "declarations": [
+              {
+                "property": "display",
+                "value": "box"
+              },
+              {
+                "property": "display",
+                "value": "flex"
+              }
+            ]
+          }
+        ]
+      }
+    ]
+  }
+}