add some c++ ketward syntax

syntax/c.jsf

@@ -459,6 +459,35 @@ done
 	"union"		struct
 	"asm"		kw
 # C++ keywords
+	#"23"
+	"constexpr"		cppkw
+	"consteval"		cppkw
+	"requires"		cppkw
+	"concept"		cppkw
+	"[[maybe_unused]]" cppkw
+	"noexcept"		cppkw
+	"alignas"		cppkw
+	"alignof"		cppkw
+	"and"		cppkw
+	"and_eq"		cppkw
+	"auto"		cppkw
+	"constinit"		cppkw
+	"co_await"		cppkw
+	"co_return"		cppkw
+	"co_yield"		cppkw
+	"decltype"		cppkw
+	"not"		cppkw
+	"not_eq"		cppkw
+	"or"		cppkw
+	"or_eq"		cppkw
+	"nullptr"		cppkw
+	"static_assert"		cppkw
+	"xor"		cppkw
+	"xor_eq"		cppkw
+	"std"			cppkw
+	"string"		type
+	"string_view"   type
+	"size_t"		type
 	#"asm"			cppkw (listed above as a C keyword)
 	"bool"			cppkw
 	"catch"			cppkw