chore: fix tests on Windows and enable it in actions

[targos]

Use a gitattributes file to force text files to be checked out with LF
line endings. This resolves issues on Windows with tests that compare
values with the contents of files on disk.

[codecov]

Codecov Report

Merging #518 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #518   +/-   ##
=======================================
  Coverage   82.49%   82.49%           
=======================================
  Files          35       35           
  Lines        1742     1742           
=======================================
  Hits         1437     1437           
  Misses        305      305           

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[targos]

macOS seems flaky :

  1 failing

  1) auth
       asks for auth data if no ncurc is found:
     Error: Timeout of 2000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves. (/Users/runner/work/node-core-utils/node-core-utils/test/unit/auth.test.js)