add gh specific build script

Author: supertommy

Diff for: .github/workflows/main.yml

@@ -19,7 +19,7 @@ jobs:
       run: npm install
 
     - name: Build
-      run: npm run build
+      run: npm run build-gh
 
     - name: Deploy
       uses: JamesIves/github-pages-deploy-action@releases/v3

Diff for: package.json

@@ -5,6 +5,7 @@
 	"scripts": {
 		"start": "parcel src/index.html -p 8000",
 		"build": "parcel build src/index.html --out-dir dist --public-url ./",
+		"build-gh": "parcel build src/index.html --out-dir dist --public-url /phaser3-typescript-spine/",
 		"test": "echo \"Error: no test specified\" && exit 1"
 	},
 	"author": "supertommy",