Add *.snk strong name key files (#2483)

* Add *.snk strong name key files

Strong name key files shouldn't be included in a repository AFAIK. they are intended to sign build output to verify that it comes from the correct publisher. having an *.snk in a repository would allow anyone to produce build as if they were the original publisher.

I guess some OSS projects might like to have *.snk files in their repos but that would be an exception to the rule.

* Make use of *.snk optional

Add note explaining use.

* Reduce explanation

Just use a link instead

VisualStudio.gitignore

@@ -219,6 +219,10 @@ ClientBin/
 *.publishsettings
 orleans.codegen.cs
 
+# Including strong name files can present a security risk 
+# (https://github.com/github/gitignore/pull/2483#issue-259490424)
+#*.snk
+
 # Since there are multiple workflows, uncomment next line to ignore bower_components
 # (https://github.com/github/gitignore/pull/1529#issuecomment-104372622)
 #bower_components/