Bump xml2js and web-ext in /webext

Bumps [xml2js](https://github.com/Leonidas-from-XIV/node-xml2js) to 0.5.0 and updates ancestor dependency [web-ext](https://github.com/mozilla/web-ext). These dependencies need to be updated together.


Updates `xml2js` from 0.4.23 to 0.5.0
- [Release notes](https://github.com/Leonidas-from-XIV/node-xml2js/releases)
- [Commits](https://github.com/Leonidas-from-XIV/node-xml2js/commits/0.5.0)

Updates `web-ext` from 7.5.0 to 7.6.1
- [Release notes](https://github.com/mozilla/web-ext/releases)
- [Commits](https://github.com/mozilla/web-ext/compare/7.5.0...7.6.1)

---
updated-dependencies:
- dependency-name: xml2js
  dependency-type: indirect
- dependency-name: web-ext
  dependency-type: direct:development
...

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

webext/package.json

@@ -23,7 +23,7 @@
     "prettier": "2.7.1",
     "sinon": "^14.0.0",
     "strip-ansi": "^7.0.1",
-    "web-ext": "^7.5.0",
+    "web-ext": "^7.6.1",
     "webpack": "^5.73.0",
     "webpack-cli": "^4.10.0"
   },