Modifiers: add icon field to ModifierTypeInfo

With this change `outliner_draw.c` does not have to be
edited anymore when a new modifier is added.

Reviewers: campbellbarton

Differential Revision: https://developer.blender.org/D8998

source/blender/modifiers/intern/MOD_normal_edit.c

@@ -785,6 +785,7 @@ ModifierTypeInfo modifierType_NormalEdit = {
     /* type */ eModifierTypeType_Constructive,
     /* flags */ eModifierTypeFlag_AcceptsMesh | eModifierTypeFlag_SupportsMapping |
         eModifierTypeFlag_SupportsEditmode | eModifierTypeFlag_EnableInEditmode,
+    /* icon */ ICON_MOD_NORMALEDIT,
 
     /* copyData */ BKE_modifier_copydata_generic,