correctly highlight @"" identifiers

credit
- ziglang@269048b

Author: atweiden

syntax/zig.vim

@@ -251,6 +251,9 @@ syntax match zigEscapeError   display contained /\\./
 syntax match zigEscape        display contained /\\\([nrt\\'"]\|x\x\{2}\)/
 syntax match zigEscapeUnicode display contained /\\\(u\x\{4}\|U\x\{6}\)/
 
+" Identifiers using the @"" syntax.
+syntax match zigIdentifierSpecial +@".*"+ display
+
 highlight default link zigDecNumber zigNumber
 highlight default link zigHexNumber zigNumber
 highlight default link zigOctNumber zigNumber