Add reaction time task

[saeub]

Closes #13

• Log events
• Collect result data
• Add tests

[codecov]

Codecov Report

Merging #14 (e85d51d) into dev (6b2454d) will decrease coverage by 12.47%.
The diff coverage is 78.88%.

@@             Coverage Diff             @@
##              dev      #14       +/-   ##
===========================================
- Coverage   63.15%   50.67%   -12.48%     
===========================================
  Files          14       21        +7     
  Lines        1460     2060      +600     
===========================================
+ Hits          922     1044      +122     
- Misses        538     1016      +478     

Impacted Files	Coverage Δ
lib/generated/intl/messages_de_CH.dart	0.00% <0.00%> (ø)
lib/main.dart	0.00% <ø> (ø)
lib/src/tasks/types.dart	47.82% <50.00%> (+0.45%)	⬆️
lib/src/tasks/reaction_time.dart	76.64% <76.64%> (ø)
lib/src/pages/task.dart	61.82% <90.62%> (+0.43%)	⬆️
lib/generated/intl/messages_en.dart	90.62% <100.00%> (+0.14%)	⬆️
lib/generated/l10n.dart	28.50% <100.00%> (+1.05%)	⬆️
lib/src/tasks/lexical_decision.dart	100.00% <100.00%> (ø)
lib/src/tasks/task.dart	100.00% <100.00%> (ø)
... and 6 more

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