update yarn ubuntu code example

Example 1: install yarn

npm install -g yarn

Example 2: yarn download ubuntu

curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
sudo apt update && sudo apt install yarn

Example 3: linux install yarn

curl -o- -L https://yarnpkg.com/install.sh | bash

Example 4: update yarn

# Windows
choco upgrade yarn

# MacOS
brew upgrade yarn

Example 5: yarn ubuntu

curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list