Replace @pierre/diffs with custom diff viewer to fix freeze

The @pierre/diffs library was causing the browser to freeze when
comparing certain versions. Implemented a simple line-based diff
that only shows added/removed lines.

package.json

@@ -9,7 +9,6 @@
     "lint": "eslint"
   },
   "dependencies": {
-    "@pierre/diffs": "^1.1.15",
     "@radix-ui/react-accordion": "^1.2.12",
     "@radix-ui/react-checkbox": "^1.3.3",
     "@radix-ui/react-collapsible": "^1.1.12",