[Security] Bump ssri from 6.0.1 to 8.0.1

Bumps [ssri](https://github.com/npm/ssri) from 6.0.1 to 8.0.1. **This update includes a security fix.**
- [Release notes](https://github.com/npm/ssri/releases)
- [Changelog](https://github.com/npm/ssri/blob/latest/CHANGELOG.md)
- [Commits](npm/ssri@v6.0.1...v8.0.1)

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

package.json

@@ -58,7 +58,7 @@
     "sass-loader": "^7.1.0",
     "semver": "^5.6.0",
     "shelljs": "^0.8.2",
-    "ssri": "^6.0.1",
+    "ssri": "^8.0.1",
     "tapable": "^2.0.0",
     "uglifyjs-webpack-plugin": "^2.0.1",
     "url-loader": "^4.1.1",