syntax/eo: add support for some more Eolian types

- generic_value
- stringshare
- promise
- void_ptr

syntax/eo.vim

@@ -12,6 +12,7 @@ syn keyword    eoType ullong int8 uint8 int16 uint16 int32 uint32 int64 uint64
 syn keyword    eoType int128 uint128 size ssize intptr uintptr ptrdiff time
 syn keyword    eoType float double ldouble bool void
 syn keyword    eoType hash string list accessor array iterator
+syn keyword    eoType generic_value stringshare promise void_ptr
 
 syn keyword    eoClassTypes class abstract interface mixin
 syn keyword    eoStructure struct enum var