--insert-pragma CLI option

v0.5.0 (05.08.2020)

Enhancements

• new --insert-pragma CLI option adds the @format pragma to all the formatted
  files that didn't have it before #75
• preserve empty lines in containers #83

Bug fixes

• correctly handle .script files like rebar.config.script #79
• export_type is formatted the same as export #86
• print type unions either all on single line or each type separated by
  | on a separate line #84