Bump is-png from 2.0.0 to 3.0.1

Bumps [is-png](https://github.com/sindresorhus/is-png) from 2.0.0 to 3.0.1.
- [Release notes](https://github.com/sindresorhus/is-png/releases)
- [Commits](sindresorhus/is-png@v2.0.0...v3.0.1)

---
updated-dependencies:
- dependency-name: is-png
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

package.json

@@ -23,7 +23,7 @@
       "gulp-rename": "^2.0.0",
       "gulp-zip": "^5.0.0",
       "image-size": "^0.7.4",
-      "is-png": "^2.0.0",
+      "is-png": "^3.0.1",
       "joi": "^14.3.1",
       "js-yaml": "^4.1.0",
       "pretty-bytes": "^5.3.0",