[Docs] Add new meshery-extensions org to label search

[miacycle]

@miacycle cloned issue meshery/meshery#14454 on 2025-04-18:

Current State

Hi everyone, Meshery has a new GitHub Organization: https://github.com/meshery-extensions. Each repository under the new organization and each repository under https://github.com/meshery organization are in need of being updated. I'm posting a message here in case any of you would like to make an easy contribution. Any number of you can perform the following task on any of the repos (all READMEs in all repos need updated).

Desired State

The new GitHub Organization meshery-extensions needs to be to add to the list of orgs hyperlinked under the "help wanted" label hyperlink. See this PR as an example of what needs to be done on other READMEs - meshery/meshsync#400. There is no need to open an issue. You can simply open a PR straight-away.

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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