Add remark-gfm for markdown table rendering in Knowledge Base

Tables are a GitHub Flavored Markdown extension not supported by
react-markdown's default parser. Added remark-gfm plugin so tables,
strikethrough, and task lists render correctly in KB articles.

frontend/package.json

@@ -15,6 +15,7 @@
     "react-scripts": "5.0.1",
     "recharts": "^3.8.1",
     "rehype-sanitize": "^6.0.0",
+    "remark-gfm": "^3.0.1",
     "web-vitals": "^2.1.4",
     "xlsx": "^0.18.5"
   },
@@ -30,7 +31,16 @@
       "react-app/jest"
     ],
     "rules": {
-      "no-unused-vars": ["warn", { "vars": "all", "args": "after-used", "ignoreRestSiblings": true, "varsIgnorePattern": "^_", "argsIgnorePattern": "^_" }]
+      "no-unused-vars": [
+        "warn",
+        {
+          "vars": "all",
+          "args": "after-used",
+          "ignoreRestSiblings": true,
+          "varsIgnorePattern": "^_",
+          "argsIgnorePattern": "^_"
+        }
+      ]
     }
   },
   "browserslist": {