Support Struct#[] and Struct#[]= typo

[ksss]

Actually, We cannot suggest from did_you_mean when typo at Struct#[] and Struct#[]= key.

Foo = Struct.new(:foo)
Foo.new[:fooo]
#=> NameError: no member 'fooo' in struct

I want to save this case.

Foo = Struct.new(:foo)
Foo.new[:fooo]
#=> NameError: no member 'fooo' in struct
Did you mean?  foo
               foo=

Now, "no member ..." message only make from here https://github.com/ksss/ruby/blob/cee9c58ef214cbbf10aedacd79c3b796eb5bba8e/struct.c#L868

[yuki24]

Thanks!