install flutter packages code example

Example 1: flutter install

$ export PATH="$PATH:`pwd`/flutter/bin"

Example 2: pubspec.yaml flutter

dependencies:
  url_launcher: ^5.4.0    # Good, any 5.4.x version where x >= 0 works.
  image_picker: '5.4.3'   # Not so good, only version 5.4.3 works.