Fix minor issue with ie11

[casperin]

In ie11, calling .set(k, v) on a map does not return the map for further chaining, so the construction in hyphenateStyleName threw an error every time in ie11. This PR should fix that, but otherwise leave the code completely unchanged.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
  • Thanks prettier
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
  • Can't find this
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov-io]

Codecov Report

Merging #14 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master    #14   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           2      2           
  Lines         122    125    +3     
  Branches       33     34    +1     
=====================================
+ Hits          122    125    +3

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

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update c4d786e...64ca893. Read the comment docs.

[frenzzy]

Thank you!

[casperin]

No problem. Keep up the good work. :-)

[casperin]

By the way, will you release this on its own? I can understand if you think it's too small -- if so I'll just keep using a local version.

[frenzzy]

Sure, just released under v3.1.0 🎉 thanks again.