Bump imagemin-webp from 6.0.0 to 8.0.0 (#160)

Bumps [imagemin-webp](https://github.com/imagemin/imagemin-webp) from 6.0.0 to 8.0.0.
- [Release notes](https://github.com/imagemin/imagemin-webp/releases)
- [Commits](https://github.com/imagemin/imagemin-webp/compare/v6.0.0...v8.0.0)

---
updated-dependencies:
- dependency-name: imagemin-webp
  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

@@ -30,7 +30,7 @@
     "gulp-sass": "^5.0.0",
     "gulp-sourcemaps": "^3.0.0",
     "gulp-uglify": "^3.0.2",
-    "imagemin-webp": "^6.0.0",
+    "imagemin-webp": "^8.0.0",
     "jshint": "^2.11.0",
     "jshint-stylish": "^2.x.x",
     "lodash.padend": "4.6.x",