Add undeclared methods

Author: soutaro

sig/annotate/rdoc_source.rbs

@@ -25,6 +25,8 @@ module RBS
                      | (TypeName, singleton_method: Symbol) -> Array[RDoc::AnyMethod]?
 
       def find_attribute: (TypeName, Symbol, singleton: bool) -> Array[RDoc::Attr]?
+
+      def class_docs: (TypeName) -> Array[::RDoc::Markup::Document | ::RDoc::Comment | ::String]?
     end
   end
 end

sig/cli.rbs

@@ -80,6 +80,8 @@ module RBS
 
     def run_subtract: (Array[String], top) -> void
 
+    def run_diff: (Array[String], LibraryOptions) -> void
+
     def test_opt: (LibraryOptions) -> String?
 
     def collection_options: (Array[String]) -> OptionParser