[Docs] Document how to generate spreadsheet credentials for Meshery

[yash37158]

Current State

Currently, there is no documentation or clear instruction on how to generate the required spreadsheet credentials for the --spreadsheet-cred flag when using the mesheryctl registry generate command

Desired State

---

Contributor Guides and Handbook

• 📚 Instructions for contributing to documentation
  • Meshery documentation site and source
• 🛠 Meshery Build & Release Strategy
• 🎨 Wireframes and designs for Meshery UI in Figma (open invite)
• 🙋🏾🙋🏼 Questions: Discussion Forum and Community Slack

[leecalcote]

Quick notes:

1. Make a copy of the Meshery Integration spreadsheet.
2. Create a GCP API token for interacting with your spreadsheet clone.
3. base64 encode your GCP API token as you provide it to the mesheryctl generate command.
   example:

$ export CRED=`cat ~/spreadsheet.json | base64`
$ cat ~/spreadsheet.json | xargs ./mesheryctl registry generate --spreadsheet-id "1DZHnzxYWOlJ69Oguz4LkRVTFM79kC2tuvdwizOJmeMw" --spreadsheet-cred

[leecalcote]

Ideally, we build support for CSV files, too.

[yash37158]

It seems that I'm unable to make a copy of the integration spreadsheet because the export options are disabled for the document.

[Aviral0702]

Please assign this docs feature to me.