[Docs] Enhance Meshery GitHub Org overview with "Extensions" section

### Current State
This page, https://github.com/meshery, does not provide information about all of Meshery's extensions and the https://github.com/meshery-extensions org.

### Desired State
Using the Meshery Extensions logo, create a section that describes the that highlights the top five most popular extensions and describes the extensions github org in general.

### Implementation
1. add the meshery extensions logo pack to this repo.
2. identify top five or six projects.
3. create an Extensions section with those projects and descriptions.
4. include links to https://meshery.io/extensions, https://github.com/meshery-extensions, and https://www.cncf.io/blog/2026/03/04/scaling-organizational-structure-with-mesherys-expanding-ecosystem/
5. Incorporate details from this [blog post](https://www.cncf.io/blog/2026/03/04/scaling-organizational-structure-with-mesherys-expanding-ecosystem/) into the new Extensions section.

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### Contributor [Guides](https://docs.meshery.io/project/contributing) and [Handbook](https://meshery.io/community#handbook)
- 📚 [Instructions for contributing to documentation](https://docs.meshery.io/project/contributing/contributing-docs)
- Meshery documentation [site](https://docs.meshery.io/) and [source](https://github.com/meshery/meshery/tree/master/docs)
- 🛠 [Meshery Build & Release Strategy](https://docs.meshery.io/project/contributing/build-and-release)
- 🎨 Wireframes and [designs for Meshery UI](https://www.figma.com/file/SMP3zxOjZztdOLtgN4dS2W/Meshery-UI) in Figma [(open invite)](https://www.figma.com/team_invite/redeem/GvB8SudhEOoq3JOvoLaoMs)
- 🙋🏾🙋🏼 Questions: [Discussion Forum](http://discuss.meshery.io) and [Community Slack](http://slack.meshery.io)