Windows installation notes

[mitchcapper]

Per #237 notes about Windows platform support for the install docs. Assuming this is what was desired will add additional docs to --allowed-modules and update https://github.com/apple/pkl-jvm-examples/pull/9 . https://github.com/apple/pkl-jvm-examples/pull/9 is mostly not related to Windows, just likely Windows users may run into issues around its usage.

I am not sure what items other than allowed-modules may specifically have path related issues or if there is a better place to discuss Windows paths in more detail.

I have not found a way to sparse-checkout (cone or no-cone) or ignore the two invalid window path areas:

• pkl-doc/src/test/files/DocGeneratorTest/output/*
• pkl-core/src/test/files/LanguageSnippetTests/input-helper/globtest/*