Bump imagemin from 7.0.1 to 8.0.1 (closes #178)

Bumps [imagemin](https://github.com/imagemin/imagemin) from 7.0.1 to 8.0.1.
- [Release notes](https://github.com/imagemin/imagemin/releases)
- [Commits](https://github.com/imagemin/imagemin/compare/v7.0.1...v8.0.1)

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

Signed-off-by: dependabot[bot] <support@github.com>

Change-Id: If3109766cccf2bb5c8edb094cd94ec55f99d660c
diff --git a/package.json b/package.json
old mode 100755
new mode 100644
index b3f9627..c372e9a
--- a/package.json
+++ b/package.json
@@ -19,7 +19,7 @@
     "grunt-sass": "^3.1.0",
     "grunt-shell": "^3.0.1",
     "grunt-terser": "^1.0.0",
-    "imagemin": "^7.0.1",
+    "imagemin": "^8.0.1",
     "optipng-bin": "^6.0.0",
     "sass": "^1.44.0",
     "vinyl-fs": "^3.0.3"