General improvements

• Remove set-env from examples:

  • The set-env command is deprecated and will be disabled on November 16th. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands/

• Added support for space separated list of files when using set-output.

• Updated action outputs (see README).