documentSymbol missing elements

[trefis]

I use the documentSymbol request to move around in .ml buffers, and just noticed that it ignores classes and class types.
Cf.

ocaml-lsp/ocaml-lsp-server/src/document_symbol.ml

Lines 224 to 232 in aae6986

	(module_decl_document_symbol pmd)
	| Psig_recmodule modules ->
	List.iter modules ~f:(iterator.module_declaration iterator)
	| Psig_modtype decl ->
	descend
	(fun () -> Ast_iterator.default_iterator.module_type_declaration iterator decl)
	(module_type_decl_symbol decl)
	| _ -> Ast_iterator.default_iterator.signature_item iterator item
	in

The linked sample concerns signature items, but the same wildcard pattern is present a few lines down for structure items.

I haven't checked if items other than classes (types) are missing, though removing the wildcard pattern should answer that.