[FEATURE] TNS command for screen recording on-device

Hey Nativescript team,

As always thanks for all the hard work -- using Nativescript Vue and enjoying it immensely!

After being thoroughly impressed by the tns resources splashes generate command, I thought it would be great to have a tns subcommand that started/stopped/extracted screen recordings from a device. It's not hard to do with recent versions of android (adb shell screenrecording /sdcard/whatever.mp4), but it might be even more convenient to use a tns command to do it (and pull out the file afterwards).

(I hope I'm filing this feature request properly -- none of the template instructions seemed to deal with feature requests, it was all about what to put for but reports...)

まず、既存の tns resources splashes generate コマンドと、CLI が Android デバイスのコマンドをどのように呼び出しているかを調べます。そのフローを adb shell screenrecording /sdcard/whatever.mp4 と比較し、生成されたファイルの取得も確認します。tns サブコマンドでデバイス上の録画を開始、停止、取り出しできれば完了です。