Add CLI docs for yarn add --exact and yarn add --tilde (#1478)
Add CLI docs for yarn add --exact and yarn add --tilde (#1478)

Descriptions were based on official docs:
https://yarnpkg.com/en/docs/cli/add
lawliet89/yarn,bsansouci/esy,kasperlewau/yarn,mgcrea/yarn,dguo/yarn,andreypopp/esy,ConAntonakos/yarn,mvestergaard/yarn,kasperlewau/yarn,mvestergaard/yarn,seripap/emojiless-yarn,lawliet89/yarn,MiguelAlho/yarn,andreypopp/esy,suitupalex/yarn,onemen/yarn,onemen/yarn,mourner/yarn,ConAntonakos/yarn,joeyespo/yarn,CHECK24/yarn,seripap/emojiless-yarn,MiguelAlho/yarn,joeyespo/yarn,bsansouci/esy,bsansouci/esy,andreypopp/esy,suitupalex/yarn,mgcrea/yarn,dguo/yarn,CHECK24/yarn,mourner/yarn