Add typings field so that TS project can identify d.ts file

Author: smikitky

package.json

@@ -4,6 +4,7 @@
   "description": "Parses and manipulates multiple comma-separated integer ranges (eg \"1-3,8-10\")",
   "repository": "https://github.com/smikitky/node-multi-integer-range.git",
   "main": "./lib/multi-integer-range.js",
+  "typings": "./lib/multi-integer-range.d.ts",
   "scripts": {
     "test": "node_modules/.bin/mocha",
     "build": "node_modules/.bin/tsc"