docs: note about existing content at same path on different branches

vintro

2023-08-14 f1c9ca495e450ecb62dade70c4b60d86e106f79c

 package.json

@@ -14,7 +14,8 @@
  "scripts": {
    "check": "tsc --noEmit && npx prettier . --check",
    "format": "npx prettier . --write",
    "test": "tsx ./quartz/path.test.ts"
    "test": "tsx ./quartz/path.test.ts",
    "profile": "0x -D prof ./quartz/bootstrap-cli.mjs build --concurrency=1"
  },
  "keywords": [
    "site generator",