Use .exe shims on Windows, not .bat

[gaborcsardi]

Closes #362.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 58.87%. Comparing base (dafa1d2) to head (6dcd7c1).

Files with missing lines	Patch %	Lines
src/shim/main.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #363      +/-   ##
==========================================
- Coverage   58.91%   58.87%   -0.04%     
==========================================
  Files          56       57       +1     
  Lines       20341    20342       +1     
==========================================
- Hits        11983    11976       -7     
- Misses       8358     8366       +8     

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