Bump extend from 1.3.0 to 3.0.2

Bumps [extend](https://github.com/justmoon/node-extend) from 1.3.0 to 3.0.2.
- [Release notes](https://github.com/justmoon/node-extend/releases)
- [Changelog](https://github.com/justmoon/node-extend/blob/main/CHANGELOG.md)
- [Commits](justmoon/node-extend@v1.3.0...v3.0.2)

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -31,7 +31,7 @@
     "mocha": "^1.21.4"
   },
   "dependencies": {
-    "extend": "^1.3.0",
+    "extend": "^3.0.2",
     "metalsmith-pagination": "^1.0.0"
   }
 }