Bump gulp-imagemin from 8.0.0 to 9.0.0 (#772)

Bumps [gulp-imagemin](https://github.com/sindresorhus/gulp-imagemin) from 8.0.0 to 9.0.0.
- [Release notes](https://github.com/sindresorhus/gulp-imagemin/releases)
- [Commits](https://github.com/sindresorhus/gulp-imagemin/compare/v8.0.0...v9.0.0)

---
updated-dependencies:
- dependency-name: gulp-imagemin
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

package.json

@@ -25,7 +25,7 @@
     "gulp-babel": "^8.0.0",
     "gulp-clean-css": "^4.3.0",
     "gulp-concat": "^2.6.1",
-    "gulp-imagemin": "^8.0.0",
+    "gulp-imagemin": "^9.0.0",
     "gulp-notify": "^4.0.0",
     "gulp-postcss": "^9.0.1",
     "gulp-rename": "^2.0.0",