Test Windows build

[osteele]

See https://ci.appveyor.com/project/osteele/gojekyll https://github.com/osteele/gojekyll/runs/5171787377?check_suite_focus=true.

This issue is reported upstream at osteele/liquid#22.

Once the Liquid issue is fixed, wellington/go-libsass#20 may be an issue.

[osteele]

The test suite shows these errors.

There appear to be three categories of errors:

• "\n" vs. "\r\n". gojekyll itself may be behaving correctly here; it might be that the fix is to set .gitattributes for the test file, or else to make the test case look for different values on Windows vs. other
• time.Location("") vs. time.Local (TestPraseFilenameData). I believe that the error is in the expected value.
• Windows vs Darwin/Linux path separators (I believe this is source of the remaining errors)