build.sh not executable after "dotnet new"

[rmunn]

Due to https://github.com/NuGet/Home/issues/4424, scripts like build.sh lose the executable permissions bit when you run dotnet new fable-library. The current solution is to add this post-action to the NuGet template to set the executable bit any script(s) in the template after it has been unzipped. A single change to Content/.template.config/template.json should do the trick; see https://github.com/TheAngryByrd/MiniScaffold/pull/37/files for an example.

I'll submit a PR for this once I have time, but it might not be until tomorrow.