add null safe operator to font locking list (#2)

Author: piotrkwiecinski

php-ts-mode.el

@@ -87,7 +87,7 @@
      "+" "++" "+=" "," "-" "-" "--" "-=" "->" "."
      ".=" "/" "/=" ":" "::" "<" "<<" "<<=" "<=" "<=>"
      "<>" "=" "==" "===" "=>" ">" ">=" ">>" ">>=" "?"
-     "?:" "??" "??=" "@" "\\" "^" "^=" "|" "|=" "||"))
+     "?:" "??" "??=" "?->" "@" "\\" "^" "^=" "|" "|=" "||"))
   "PHP operators for tree-sitter font-locking.")
 
 (defconst php-ts-mode--magical-constants