Build get files command

[edwtorba]

Ticket:

• Create command local:files:get

Description:

• Implements the command get-files.
• Update the documentation.
• Include the command get-files into the command local:build.

How to test:

• Create and configure a project with lando or ddev.
• Configure the environment parameters: remote_platform, remote_sitename and remote_canonical_env.
• Run the following command: fire get-files or fire pull-files.
• Then run the following command: ls -lha web/sites/default/files and check that the website's files were downloaded.