* ci: add dependabot
* ci: revamp logic
Merge username and password as a single auth token. It doesn't make
sense to split out the user and password since they are so tied
together. Might as well treat the whole think as a secret blob.
Remove Travis-CI. Travis is dead for OSS.
Add GitHub Actions cron. Remove cachix as it's pushing too much stuff.
Merge all of the CI logic into a single ci.sh script.
