Add backing type of a `bit_field` to the doc-format

core/odin/doc-format/doc_format.odin

@@ -251,6 +251,7 @@ Type :: struct {
 	// .Multi_Pointer      - 1 type:    0=element
 	// .Matrix             - 1 type:    0=element
 	// .Soa_Pointer        - 1 type:    0=element
+	// .Bit_Field          - 1 type:    0=backing type
 	types: Array(Type_Index),
 
 	// Used by:

src/docs_writer.cpp

@@ -625,6 +625,7 @@ gb_internal OdinDocTypeIndex odin_doc_type(OdinDocWriter *w, Type *type) {
 				fields[i] = odin_doc_add_entity(w, type->BitField.fields[i]);
 			}
 			doc_type.entities = odin_write_slice(w, fields.data, fields.count);
+			doc_type.types = odin_doc_type_as_slice(w, type->BitField.backing_type);
 		}
 		break;