syntax highlighting for pdf type (#2414)

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> [!IMPORTANT]
> Add `pdf` to recognized types in `type_definition` pattern in
`baml.tmLanguage.json`.
> 
>   - **Syntax Highlighting**:
> - Add `pdf` to recognized types in `type_definition` pattern in
`baml.tmLanguage.json`.
> 
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Author: imalsogreg

typescript/apps/vscode-ext/syntaxes/baml.tmLanguage.json

@@ -350,7 +350,7 @@
     "type_definition": {
       "patterns": [
         {
-          "match": "\\b(bool|int|float|string|null|image|audio)\\b",
+          "match": "\\b(bool|int|float|string|null|image|audio|pdf)\\b",
           "name": "storage.type.baml"
         },
         {