add to markdown-it plugin directory

package.json

 {
   "name": "markdown-it-katex",
-  "version": "1.0.2",
+  "version": "1.0.3",
   "description": "Easy KaTeX support for markdown-it ",
   "main": "index.js",
   "scripts": {
@@ -11,7 +11,8 @@
     "markdown",
     "KaTeX",
     "math",
-    "LaTeX"
+    "LaTeX",
+    "markdown-it-plugin"
   ],
   "author": "waylonflinn@gmail.com",
   "license": "MIT",