Support DXT Extension format

[Flux159]

It seems like Anthropic is looking to make MCP server installation easier with DXT (Desktop Extensions): https://github.com/anthropics/dxt

We should support building to this format so that users don't need to change claude_desktop_config.json and will be able to install using this zip like format.

This should be relatively simple to add into cd.yml, but need to confirm about code signing.

[Flux159]

More about this: https://www.anthropic.com/engineering/desktop-extensions

[Flux159]

The dxt is being created via cd.yml now, but there's still the manual process of uploading the dxt to Anthropic which I opened up an issue for in modelcontextprotocol/mcpb#3. I submitted version 2.4.5 to Anthropic via the google form already, but ideally don't want to do this manually for every release.

Also investigating the format a bit more to see if we need to pass env var options & the .kube directory needs to be explicitly specified as a directory in #166.

[Flux159]

This version should work with default kube config at ~/.kube/config - https://github.com/Flux159/mcp-server-kubernetes/releases/tag/v2.5.0

Will need to make some code changes for adding env var support. There's also a tilde path expansion issue for user provided arguments / env vars in modelcontextprotocol/mcpb#37 so might be best to hold off on adding that support until there's a fix for that to avoid bug reports here.