Bump web-ext from 3.2.1 to 4.0.0

Bumps [web-ext](https://github.com/mozilla/web-ext) from 3.2.1 to 4.0.0.
- [Release notes](https://github.com/mozilla/web-ext/releases)
- [Commits](https://github.com/mozilla/web-ext/compare/3.2.1...4.0.0)

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

package.json

@@ -43,7 +43,7 @@
     "typescript": "^3.7.4",
     "uglify-es": "^3.3.9",
     "uglifyjs-webpack-plugin": "^2.2.0",
-    "web-ext": "^3.2.1",
+    "web-ext": "^4.0.0",
     "web-ext-types": "^3.2.1",
     "webpack": "^4.41.4",
     "webpack-cli": "^3.3.10"