Test AppSettingsModal component

[AWolf81]

Related Issue:
#309

Summary:
Added tests for AppSettingsModal

• Updating activeField
• Saving newSettings
• Dialog test if path does't exists
• Snapshot for rendering

[codecov]

Codecov Report

Merging #371 into master will increase coverage by 3.42%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #371      +/-   ##
==========================================
+ Coverage   52.35%   55.78%   +3.42%     
==========================================
  Files         158      158              
  Lines        3335     3304      -31     
  Branches      458      458              
==========================================
+ Hits         1746     1843      +97     
+ Misses       1362     1247     -115     
+ Partials      227      214      -13

Impacted Files	Coverage Δ
...rc/components/AppSettingsModal/AppSettingsModal.js	96% <ø> (+96%)	⬆️
src/utils.js	39.43% <0%> (+5.63%)	⬆️
src/components/TextInput/TextInput.js	100% <0%> (+10%)	⬆️
src/components/FormField/FormField.js	100% <0%> (+12.5%)	⬆️
...nents/ProjectTypeSelection/ProjectTypeSelection.js	72.72% <0%> (+27.27%)	⬆️
src/components/Heading/Heading.js	75% <0%> (+33.33%)	⬆️
src/components/DirectoryPicker/DirectoryPicker.js	46.15% <0%> (+46.15%)	⬆️
src/components/PixelShifter/PixelShifter.js	100% <0%> (+50%)	⬆️
src/components/ModalHeader/ModalHeader.js	100% <0%> (+57.14%)	⬆️
src/components/ScrollDisabler/ScrollDisabler.js	59.09% <0%> (+59.09%)	⬆️
... and 3 more

[superhawk610]

Looks great! Getting that coverage closer to 100% every day.