Allow /mcp page to also list extensions to be installed

[digitarald]

Some of the 1p MCPs are being packaged as extensions; and they prefer to link to extensions instead of the MCPs.

[digitarald]

cc @isidorn for input.

[isidorn]

@digitarald this makes sense to me. The question is if we:

1. List all the extensions on https://code.visualstudio.com/mcp
2. Just link to Marketplace and point to Marketplace search that filters down to extensions that provide an MCP. E.g. something like (but maybe we have a new tag) https://marketplace.visualstudio.com/search?term=tag%3Alanguage-model-tools&target=VSCode&category=All%20categories&sortBy=Relevance

The 2) is easy to do, and I would probably start with that

[ntrogh]

@sandy081 added support for including extensions on the /mcp page. Some configs were already updated to install the extension (e.g. Context7, Codacy, Azure).