[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...)

先檢查現有的 tns resources splashes generate 命令，以及 CLI 如何呼叫 Android 裝置命令。將該流程與 adb shell screenrecording /sdcard/whatever.mp4 進行比較，包括取得產生的檔案。完成標準是：一個 tns 子命令可以啟動、停止並擷取裝置上的錄製內容。