Update dependency prettier to ~2.8.0 (#490)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

package-lock.json

@@ -81,7 +81,7 @@
         "mocha-chai-jest-snapshot": "^1.1.3",
         "nyc": "^15.1.0",
         "pako": "^2.1.0",
-        "prettier": "~2.7.0",
+        "prettier": "~2.8.0",
         "stylelint": "^14.9.1",
         "stylelint-config-standard-vue": "^1.0.0",
         "ts-node": "^10.2.1",