Deprecate `plugins` command

Is your feature request related to a problem? Please describe.

No response

Describe the solution you'd like

To simplify, per discussion with @rigor789 in Discord.

Describe alternatives you've considered

Devs can use their package manager directly to install plugins: npm install <foo>, etc.

Anything else?

I'd suggest any reference to ns plugin install in docs be changed to only mention NPM's install command: "npm install <foo> or as appropriate for your package manager", to reduce docs maintenance. Users of other package managers know the analogous command for their package manager.

Please accept these terms

• I have searched the existing issues as well as StackOverflow and this has not been posted before
• I agree to follow this project's Code of Conduct

まず、plugins コマンドの実装と、ns plugin install へのドキュメント内のすべての参照を見つけます。この issue にはファイルパスやテストパスがありません。プロジェクトで意図されている非推奨化の動作を確認し、パッケージマネージャーの表現に合わせて参照を更新し、コマンドとドキュメントがその決定を一貫して反映していることを検証します。