Added short-flags for yarn add (#1618)
Added short-flags for yarn add (#1618)

* Added short flags in yarn add command

* Fixed commander signature for add

bsansouci/esy,kasperlewau/yarn,lawliet89/yarn,mourner/yarn,andreypopp/esy,mvestergaard/yarn,suitupalex/yarn,onemen/yarn,seripap/emojiless-yarn,dguo/yarn,ConAntonakos/yarn,seripap/emojiless-yarn,bsansouci/esy,suitupalex/yarn,dguo/yarn,lawliet89/yarn,CHECK24/yarn,bsansouci/esy,mgcrea/yarn,joeyespo/yarn,andreypopp/esy,CHECK24/yarn,kasperlewau/yarn,mvestergaard/yarn,andreypopp/esy,mourner/yarn,joeyespo/yarn,onemen/yarn,mgcrea/yarn,ConAntonakos/yarn