Update package.json - bump version

I bumped from `1.2.0` to `1.3.0` because I would not consider this a fix, rather an additional feature.

Author: nickgraffis

package.json

@@ -11,7 +11,7 @@
     "virtual-list",
     "virtual-scroll"
   ],
-  "version": "1.2.0",
+  "version": "1.3.0",
   "repository": {
     "type": "git",
     "url": "git+https://github.com/v1ack/svelte-virtual-scroll-list.git"