A `publish` directory for a C# binary contains copies of some DLLs
inside localized subdirectories (e.g. `ru`). We want to ignore those, as
otherwise our packaging machinery now goes haywire, with the newer
version of `rules_csharp`. In any case we never shipped those.
This commits a bazel-based build system for C#
using `rules_dotnet`. External dependencies are managed
via `paket`, and updates to the generated bazel files
are done via `./update-deps.sh`.
We're providing our own (minimal) test runner for `xunit`
tests.
