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

[shazron]

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?