replace react-shiki with react-syntax-highlighter to reduce package size

lightrag_webui/package.json

@@ -50,7 +50,7 @@
     "react-dropzone": "^14.3.6",
     "react-markdown": "^9.1.0",
     "react-number-format": "^5.4.3",
-    "react-shiki": "^0.3.0",
+    "react-syntax-highlighter": "^15.6.1",
     "rehype-react": "^8.0.0",
     "remark-gfm": "^4.0.1",
     "remark-math": "^6.0.0",
@@ -69,6 +69,7 @@
     "@types/node": "^22.13.5",
     "@types/react": "^19.0.10",
     "@types/react-dom": "^19.0.4",
+    "@types/react-syntax-highlighter": "^15.5.13",
     "@types/seedrandom": "^3.0.8",
     "@vitejs/plugin-react-swc": "^3.8.0",
     "eslint": "^9.21.0",