update yarn packages code example

Example 1: yarn update all dependencies to latest

yarn upgrade --latest

Example 2: yarn update all packages

yarn upgrade --latest
yarn upgrade left-pad --latest
yarn upgrade left-pad grunt --latest --tilde

Example 3: yarn update a specific package

yarn upgrade
yarn upgrade left-pad
yarn upgrade left-pad@^1.0.0
yarn upgrade left-pad grunt
yarn upgrade @angular