Merge pull request #7920 from github/hmac/string-flow-summaries

Ruby: Add String flow summaries

Author: hmac

ruby/ql/lib/codeql/ruby/frameworks/Core.qll

@@ -10,6 +10,7 @@ import core.Object::Object
 import core.Kernel::Kernel
 import core.Module
 import core.Array
+import core.String
 import core.Regexp
 
 /**