Add Kmesh and Volcano plugin cards to Available Plugins page

Description

• Add plugin cards for Kmesh and Volcano to Headlamp’s Available Plugins page.
• The new cards should follow the existing plugin card design and layout used on the page.

Kmesh Headlamp Plugin: https://github.com/headlamp-k8s/plugins/tree/main/kmesh Volcano Headlamp Plugin: https://github.com/headlamp-k8s/plugins/tree/main/volcano

Website Page: https://headlamp.dev/plugins