C#: Add comment justifing turning off strict deps.

Author: criemen

.bazelrc.internal

@@ -3,4 +3,8 @@
 common --registry=file:///%workspace%/ql/misc/bazel/registry
 common --registry=https://bcr.bazel.build
 
+# See bazelbuild/rules_dotnet#413: strict_deps in C# also appliy to 3rd-party deps, and when we pull
+# in (for example) the xunit package, there's no code in this at all, it just depends transitively on
+# its implementation packages without providing any code itself.
+# We either can depend on internal implementation details, or turn of strict deps.
 common --@rules_dotnet//dotnet/settings:strict_deps=false