Implemented const keyword

src/errors/Common.go

@@ -2,6 +2,7 @@ package errors
 
 var (
 	EmptySwitch                = &Base{"Empty switch"}
+	ExpectedConstName          = &Base{"Expected a name for the const group"}
 	ExpectedFunctionParameters = &Base{"Expected function parameters"}
 	ExpectedFunctionDefinition = &Base{"Expected function definition"}
 	ExpectedIfBeforeElse       = &Base{"Expected an 'if' block before 'else'"}