Only build the js on release (#43)

Author: matthewp

package.json

@@ -9,7 +9,7 @@
   "scripts": {
     "build": "make astro-wasm && lerna run build --scope @astrojs/compiler",
     "build:compiler": "lerna run build --scope @astrojs/compiler",
-    "prerelease": "yarn build",
+    "prerelease": "yarn build:compiler",
     "release": "changeset publish"
   },
   "workspaces": [