fix: nonbreaking space in control

[erdos]

As mentioned in #139 (comment)

The most nasty issue we've got probably. We've had a long DOCX template which included {% end %} tag that contained a Non-breaking space between d and % which failed the rendering. It was only returning stencil.exceptions.ParsingException: Unexpected command I believe.

Apparently, java.lang.Character/isWhitespace is false for non-breaking whitepsace and therefore java.lang.String/trim also does not work on it. It produces cryptic error messages so lets fix it properly.

[codecov]

Codecov Report

Merging #141 (dad60d2) into master (858b1e2) will decrease coverage by 0.16%.
The diff coverage is 73.33%.

@@            Coverage Diff             @@
##           master     #141      +/-   ##
==========================================
- Coverage   92.08%   91.91%   -0.17%     
==========================================
  Files          26       26              
  Lines        1894     1905      +11     
  Branches      106      109       +3     
==========================================
+ Hits         1744     1751       +7     
- Misses         44       45       +1     
- Partials      106      109       +3     

Impacted Files	Coverage Δ
src/stencil/infix.clj	87.29% <0.00%> (-0.56%)	⬇️
src/stencil/util.clj	95.40% <72.72%> (-3.29%)	⬇️
src/stencil/postprocess/list_ref.clj	92.34% <100.00%> (ø)
src/stencil/tokenizer.clj	96.82% <100.00%> (ø)

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