Add PowerShell syntax test

[dp304]

Part of the work for issue #1213.

A short PowerShell script and the corresponding syntax-highlighted output
has been added. The script exhibits many of the peculiarities of the
PowerShell syntax.

[dp304]

The added source file appears in the repo as binary, because it is in UTF-16 big endian format, complete with that silly BOM (U+FEFF) at the beginning.
This is how PowerShell ISE (on Win7) saved it, so I guess this is the way it's authentic, but please let me know if it should be converted.

[sharkdp]

Thank you very much for your contribution!

The added source file appears in the repo as binary, because it is in UTF-16 big endian format, complete with that silly BOM (U+FEFF) at the beginning.
This is how PowerShell ISE (on Win7) saved it, so I guess this is the way it's authentic, but please let me know if it should be converted.

Sounds good to me. bat can handle UTF-16 just fine, so this seems like a good additional test.

[dp304]

Thanks for merging! Can you please add the hacktoberfest-accepted label?