Docker container Arm builds

For Raspberry Pis, etc.

External issues:
* https://github.com/JakeWharton/plex-auto-trash/issues/1

Projects:
* [ ] `JakeWharton/docker-mbsync`
* [x] `JakeWharton/gitout`
* https://github.com/JakeWharton/gitout/pull/319
* [x] `JakeWharton/hardcover-data-sync`
* https://github.com/JakeWharton/hardcover-data-sync/pull/107
* [x] `JakeWharton/plex-auto-trash`
* https://github.com/JakeWharton/plex-auto-trash/pull/62
* [x] `JakeWharton/plex-orphaned-files`
* https://github.com/JakeWharton/plex-orphaned-files/pull/53
* [ ] `JakeWharton/qbt-orphaned-downloads`
* [ ] `JakeWharton/qbt-tracker-hound`
* [ ] `JakeWharton/qbt-seed-type`
* [x] `JakeWharton/radarr-folder-fixer`
* https://github.com/JakeWharton/radarr-folder-fixer/pull/28
* [x] `JakeWharton/singular-solution`
* https://github.com/JakeWharton/singular-solution/pull/120

Start by reviewing the unchecked projects in the issue: docker-mbsync, qbt-orphaned-downloads, qbt-tracker-hound, and qbt-seed-type. Compare their current container build configuration with the completed projects and review the linked external issue and pull requests for context. Done means the remaining project entries support Arm container builds and can be checked off with the relevant pull requests linked.

Written by the indexing model from the issue text.