doc: add note about autocrlf required for tests

Adds a note to test/README.md that setting autocrlf to true when
checking out sources is required for the tests to run successfully.

PR-URL: https://github.com/nodejs/node/pull/20752
Ref: https://github.com/nodejs/node/issues/18967
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>

test/README.md

@@ -8,6 +8,9 @@ directory, see [the guide on writing tests](../doc/guides/writing-tests.md).
 On how to run tests in this directory, see
 [the contributing guide](../doc/guides/contributing/pull-requests.md#step-6-test).
 
+For the tests to successfully run on Windows, Node.js has to be checked out from
+GitHub with the `autocrlf` git config flag set to true.
+
 ## Test Directories
 
 |Directory          |Runs on CI     |Purpose        |