fix(errors): handle errors that aren't syntax errors

[robwise]

Previously, we were assuming all errors thrown during execution of the formatters were going to be
syntax errors. However, this is not the case, so we must handle these errors elegantly by displaying
them in a popup.

Resolves #231

[codecov-io]

Codecov Report

Merging #240 into master will increase coverage by 0.22%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #240      +/-   ##
==========================================
+ Coverage      76%   76.23%   +0.22%     
==========================================
  Files          26       26              
  Lines         421      425       +4     
  Branches       40       40              
==========================================
+ Hits          320      324       +4     
  Misses         87       87              
  Partials       14       14

Impacted Files	Coverage Δ
src/executePrettier/handleError.js	100% <100%> (ø)	⬆️

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