Add npm command

[vimode]

This PR adds the slash command for /npm command, which accepts a package name a required option.

It will show errors if its unable to fetch anything from npm (if npm is down!) and will also show an error if no results are found that are closest to the search query.

On successfully fetching the package, it will display the package name, version, npm link, description, author name if any and the list of maintainers as an embed.

Let me know if there needs to be any fixes or addition to the command's output.

Thank you.

[sonarcloud[bot]]

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