Add the props file from Statiq.Web to Statiq.Docs

[daveaglick]

It does not appear to be restoring transitively and instead of spending hours debugging that behavior it's probably easier to just copy over the props file into the Statiq.Docs package

[daveaglick]

Added a props file, but it doesn't appear to be having an impact (at least not as far as excluding folders like the theme folder is concerned). Will need to do some build logging and further research.

[daveaglick]

This is now resolved with Statiq Docs version 1.0.0-beta.5. It turns out that the .props file was being included correctly, but the timing of .props imports put it before the SDK figured out the paths to include (thus overwriting the exclusions from the .props file). Changing it to a .targets file resolved the issue.