Add build script

package.json

@@ -3,6 +3,7 @@
   "version": "0.1.0",
   "description": "A CSS preprocessor with a Lisp-inspired syntax",
   "scripts": {
+    "build": "tsc",
     "test": "ts-node ./node_modules/.bin/tape ./src/tests/**/*.test.ts | tap-dot",
     "prettier": "prettier --write ./**/*.ts"
   },