Fix CallExtensionAsync parse

[ogonkov]

Summary

Proposed change:

Fix parsing of async extensions. It's treated as filter now, and looks like old typo.

Checklist

I've completed the checklist below to ensure I didn't forget anything. This makes reviewing this PR as easy as possible for the maintainers. And it gets this change released as soon as possible.

• Proposed change helps towards purpose of this project.
• Documentation is added / updated to describe proposed change.
• Tests are added / updated to cover proposed change.
• Changelog has an entry for proposed change (if user-facing fix or feature).

[codecov]

Codecov Report

Merging #1357 (8df0dae) into master (d34fdbf) will increase coverage by 0.16%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1357      +/-   ##
==========================================
+ Coverage   89.65%   89.82%   +0.16%     
==========================================
  Files          22       22              
  Lines        3046     3046              
==========================================
+ Hits         2731     2736       +5     
+ Misses        315      310       -5     

Impacted Files	Coverage Δ
nunjucks/src/transformer.js	98.90% <ø> (ø)
nunjucks/src/compiler.js	96.72% <0.00%> (+0.86%)	⬆️

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[ogonkov]

Very strange, this tests runs locally without any problems.

[brettdewoody]

The error seems to be a missing module at ../src/precompile. This looks like an incorrect relative path in bin/compile.

I believe the import should be ../nunjucks/src/precompile. And there's another import in that same file (../src/environment) which should be ../nunjucks/src/environment