zsh/extras/aliases.zsh: Add alias ytp for portable youtube-dl
zsh/extras/aliases.zsh: Add alias ytp for portable youtube-dl

Limit to DASH MP4/H.264 and M4A/AAC if at all possible, so as to be
portable (which to me basically means natively playable on iOS).

zmwangx/dotfiles,zmwangx/dotfiles,zmwangx/dotfiles,zmwangx/dotfiles,zmwangx/dotfiles