Update `Supporting Tools and Services` to include the latest MCP customization features

[AlvaroRausell]

As per version 0.80.0 of the devcontainer CLI, MCPs are part of the spec and can be defined by adding a customization option in the .devcontainer.json file. This information is made available in the VS Code website. It would be useful to have this made available in containers.dev, more specifically in the Supporting Tools and Services page, where other such settings are mentioned.

[dfberry]

@bamurtaugh Just so I understand, the devcontainer spec for mcp in dev container is complete, and the VSCode documentation for same is complete, only the devcontainer website is missing the feature documentation? Is that correct? I'm happy to provide that.

[bamurtaugh]

As potentially a slight clarification, the MCP config support is specifically part of the VS Code customization part of devcontainer.json and devcontainer-feature.json (what's shown in https://code.visualstudio.com/updates/v1_102#_dev-container-support-for-mcp-configuration).

Getting a PR would be fantastic - I'm more than happy to review. Thank you so much!