chore(deps): bump webextension-polyfill from 0.11.0 to 0.12.0

Bumps [webextension-polyfill](https://github.com/mozilla/webextension-polyfill) from 0.11.0 to 0.12.0.
- [Release notes](https://github.com/mozilla/webextension-polyfill/releases)
- [Commits](mozilla/webextension-polyfill@0.11.0...0.12.0)

---
updated-dependencies:
- dependency-name: webextension-polyfill
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

package.json

@@ -5,7 +5,7 @@
  "main": "bundle.js",
  "dependencies": {
  "d3-time-format": "^4.1.0",
- "webextension-polyfill": "^0.11.0"
+ "webextension-polyfill": "^0.12.0"
  },
  "devDependencies": {
  "@types/d3-time-format": "^4.0.3",