fix: upgrade sharp from 0.26.3 to 0.28.1

Snyk has created this PR to upgrade sharp from 0.26.3 to 0.28.1.

See this package in npm:
https://www.npmjs.com/package/sharp

See this project in Snyk:
https://app.snyk.io/org/kadirselcuk/project/6734acfa-d4f2-4cf0-b195-3a6da43088a6?utm_source=github&utm_medium=upgrade-pr

Author: snyk-bot

package-lock.json

@@ -67,7 +67,7 @@
     "readdirp": "^3.5.0",
     "recursive-readdir-sync": "^1.0.6",
     "rimraf": "^2.7.1",
-    "sharp": "^0.26.3",
+    "sharp": "^0.28.1",
     "sinon": "^7.2.2",
     "slugg": "^1.1.0",
     "yaml": "^1.9.2"