Add extra-files to release please (#80)

Author: matthewelwell

release-please-config.json

@@ -8,7 +8,10 @@
             "bump-patch-for-minor-pre-major": false,
             "draft": false,
             "prerelease": false,
-            "include-component-in-tag": false
+            "include-component-in-tag": false,
+            "extra-files": [
+                "FlagsmithClient.podspec"
+            ]
         }
     },
     "$schema": "https://raw.githubusercontent.com/googleapis/release-please/main/schemas/config.json",