fix: fix multiapps tasks (#231)

* Update JSON example for multi_apps: change snapshot name and specify presenter in instructions for clarity.

* Enhance PDF image comparison in chrome.py by adding existence checks for input files and improving image extraction logic. Introduce image hashing for similarity scoring with a configurable threshold. Update docs.py to support fuzzy matching in DOCX file comparisons, allowing for similarity scoring based on text content. Modify example JSON to enable fuzzy matching option.

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Co-authored-by: yuanmengqi <yuanmengqi@mail.ustc.edu.cn>

evaluation_examples/examples/multi_apps/aad10cd7-9337-4b62-b704-a857848cedf2.json

@@ -65,6 +65,9 @@
       "type": "vm_file",
       "path": "/home/user/Desktop/notes.docx",
       "dest": "notes.docx"
+    },
+    "options": {
+      "fuzzy_match": true
     }
   },
   "proxy": false