docs(plugins): add semantic-release-firefox

docs/extending/plugins-list.md

@@ -53,3 +53,7 @@
   - [verifyConditions](https://github.com/GabrielDuarteM/semantic-release-chrome#verifyconditions) Verify the presence of the authentication (set via environment variables).
   - [prepare](https://github.com/GabrielDuarteM/semantic-release-chrome#prepare) Write the correct version to the manifest.json and creates a zip file of the whole dist folder.
   - [publish](https://github.com/GabrielDuarteM/semantic-release-chrome#publish) Uploads the generated zip file to the webstore, and publish the item.
+- [semantic-release-firefox](https://github.com/felixfbecker/semantic-release-firefox) Set of semantic-release plugins for publishing a Firefox extension release.
+  - [verifyConditions](https://github.com/felixfbecker/semantic-release-firefox#verifyconditions) Verify the presence of the authentication (set via environment variables).
+  - [prepare](https://github.com/felixfbecker/semantic-release-firefox#prepare) Write the correct version to the manifest.json,   creates a xpi file of the dist folder and a zip of the sources.
+  - [publish](https://github.com/felixfbecker/semantic-release-firefox#publish) Submit the generated archives to the webstore for review, and publish the item including release notes.