feature/type-declarations (#1)

Co-authored-by: Jack Hadrill <jack@hadrill.co.uk>
Reviewed-on: https://git.jacknet.io/TerribleCodeClub/romulus-js/pulls/1
Co-authored-by: Jack Hadrill <jackhadrill@git.jacknet.io>
Co-committed-by: Jack Hadrill <jackhadrill@git.jacknet.io>

package.json

@@ -2,11 +2,13 @@
   "name": "romulus-js",
   "version": "1.0.0",
   "description": "An implementation of the Romulus-M cryptography specification.",
-  "main": "index.js",
+  "main": "dist/index.js",
+  "types": "dist/index.d.ts",
   "scripts": {
     "lint": "ts-standard",
     "test": "jest",
-    "build": "tsc"
+    "build": "tsc",
+    "postinstall": "tsc"
   },
   "repository": {
     "type": "git",