Update metadata

Author: wooorm

package.json

@@ -1,13 +1,17 @@
 {
   "name": "mdast-util-assert",
   "version": "2.0.1",
-  "description": "Assert mdast nodes",
+  "description": "mdast utility to assert trees",
   "license": "MIT",
   "keywords": [
-    "assert",
+    "unist",
     "mdast",
+    "mdast-util",
     "util",
-    "utility"
+    "utility",
+    "assert",
+    "check",
+    "test"
   ],
   "repository": "syntax-tree/mdast-util-assert",
   "bugs": "https://github.com/syntax-tree/mdast-util-assert/issues",