chore: update zmodel prism definition (#529)

Author: ymc9

src/lib/prism-zmodel.js

@@ -1,5 +1,5 @@
 Prism.languages.zmodel = Prism.languages.extend('clike', {
-    function: /@@?[A-Za-z_]\w*/,
+    function: /@@*[A-Za-z_]\w*/,
     keyword: /\b(?:datasource|enum|generator|model|type|abstract|import|extends|attribute|view|plugin|proc|with)\b/,
     entity: /\b(?:Int|String|Boolean|DateTime|Float|Decimal|BigInt|Bytes|Json|Unsupported)\b/,
     'type-class-name': /(\b()\s+)[\w.\\]+/,