Update fetch-secrets.sh in /main/src/pages/guides/app_builder_guides/deployment/cicd-using-github-actions.md

Added an improved version of `fetch-secrets.sh` here: https://gist.github.com/shazron/88a1c2794584d7a834b8447a92f88989
Used Cursor+sonnet.

Improvements:
- checks for `jq` being installed and gives instructions on how to install it
- adds the `_PROD` or `_STAGE` suffixes to the env vars based on the workspace (non-prod is _STAGE)
- outputs the key+values in a dotenv format
- this dotenv format can be used to automatically set the secrets via the Github CLI. Instructions are provided at the end of the script how to add them

@theManikJindal WDYT? Shall I send a PR?

Open main/src/pages/guides/app_builder_guides/deployment/cicd-using-github-actions.md and compare its current fetch-secrets.sh with the version in the linked gist. Check the existing document's surrounding instructions, then update the script and verify that the jq guidance, workspace suffixes, dotenv output, and GitHub CLI instructions are all represented.

Written by the indexing model from the issue text.