Update config.json (#9603)

fix: 🦋 error Error: Failed to find where HEAD diverged from master. Does
master exist?

happen when try to run changeset command with the default config .

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examples/with-changesets/.changeset/config.json

@@ -1,6 +1,7 @@
 {
   "$schema": "https://unpkg.com/@changesets/[email protected]/schema.json",
   "changelog": "@changesets/cli/changelog",
+  "baseBranch": "main",
   "commit": false,
   "fixed": [],
   "linked": [],