lint: add newlines per Rubocop -a

[mburns]

What

• run rubocop -a
• add rubocop_todo.yml for future use.

[codecov-io]

Codecov Report

Merging #120 into master will not change coverage. The diff coverage is n/a.

@@          Coverage Diff          @@
##           master   #120   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          15     15           
  Lines         154    154           
=====================================
  Hits          154    154

Impacted Files	Coverage Δ
test/unit/spec/roundcube_spec.rb	100% <ø> (ø)	:arrow_up:
test/unit/spec/wallabag_spec.rb	100% <ø> (ø)	:arrow_up:
test/unit/spec/_system_spec.rb	100% <ø> (ø)	:arrow_up:
test/unit/spec/dkim_spec.rb	100% <ø> (ø)	:arrow_up:
test/unit/spec/clamav_spec.rb	100% <ø> (ø)	:arrow_up:
test/unit/spec/_web_spec.rb	100% <ø> (ø)	:arrow_up:
test/unit/spec/amavis_spec.rb	100% <ø> (ø)	:arrow_up:
test/unit/spec/_email_spec.rb	100% <ø> (ø)	:arrow_up:
test/unit/spec/postfix_spec.rb	100% <ø> (ø)	:arrow_up:
test/unit/spec/_multimedia_spec.rb	100% <ø> (ø)	:arrow_up:
... and 5 more

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