chore: update config template (#15344)

.docker/selfhost/config.json.example

@@ -0,0 +1,14 @@
+{
+  "$schema": "https://github.com/toeverything/affine/releases/latest/download/config.schema.json",
+  "server": {
+    "name": "AFFiNE Self-hosted",
+    "externalUrl": "http://localhost:3010"
+  },
+  "copilot": {
+    "enabled": true,
+    "byok": {
+      "enabled": true,
+      "allowCustomEndpoint": true
+    }
+  }
+}