chore(deps): bump lodash from 4.17.15 to 4.17.21

Bumps [lodash](https://github.com/lodash/lodash) from 4.17.15 to 4.17.21.
- [Release notes](https://github.com/lodash/lodash/releases)
- [Commits](lodash/lodash@4.17.15...4.17.21)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

package-lock.json

@@ -34,7 +34,7 @@
     "hexo-server": "^0.3.3",
     "hexo-util": "^0.6.3",
     "hexo-wordcount": "6.0.1",
-    "lodash": "^4.17.11",
+    "lodash": "^4.17.21",
     "lunr": "github:codepiano/lunr.js.git"
   },
   "devDependencies": {