Fix #321 by allowing question marks in type params

[danez]

Q	A
Bug fix?	yes
Breaking change?	no
New feature?	no
Deprecations?	no
Spec compliancy?	no
Tests added/pass?	yes
Fixed tickets	Fixes #321
License	MIT

This reverses the logic of the loop inside flowParseFunctionTypeParams, which does not only allow name tokens but any token besides parenR and ellipsis.

//cc @gabelevi

[codecov-io]

Codecov Report

Merging #338 into master will increase coverage by <.01%.

@@            Coverage Diff             @@
##           master     #338      +/-   ##
==========================================
+ Coverage   97.65%   97.65%   +<.01%     
==========================================
  Files          20       20              
  Lines        3326     3327       +1     
  Branches      882      883       +1     
==========================================
+ Hits         3248     3249       +1     
  Misses         30       30              
  Partials       48       48

Impacted Files	Coverage Δ
src/plugins/flow.js	97.53% <100%> (ø)	✅

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