Switch to using Taskcluster instead of Travis CI

We're opening this issue because your project has used Travis CI within the last 6 months. If you have already migrated off it, you can close and ignore this issue.

Travis CI is ending free builds on public repositories. travis-ci.com stopped providingthem in early November, and travis-ci.org will stop after December 31, 2020. To avoid disruptions to your workflows, you must migrate to another CI service.

For production use cases, we recommend switching to CircleCI. This service is already widely used within Mozilla. There is a guide to migrating from Travis CI to CircleCI available here.

For non production use cases, we recommend either CircleCI or Github Actions. There is a guide to migrating from Travis CI to Github Actions available here. Github Actions usage within Mozilla is new, and you will have to work with our github administrators to enable specific actions following this process.

If you have any questions, reach out in #github-admin:mozilla.org on matrix.