`IntelliJ | Install Azure MCP Server` badge

[joshfree]

Describe the bug

It's awesome having install badges for 3 of our 4 IDE extensions now:

But we're missing the IntelliJ plugin. Can we add an install badge for it?

Expected behavior

All IDE Extensions/Plugins have badges on both the root /README.md and the /servers/Azure.Mcp.Server/README.md

[joshfree]

Tagging @srnagar who added the IntelliJ plugin

[srnagar]

Done in #593