update outdated GH actions

[orbeckst]

• PR add dependabot config for GH actions #508 set up dependabot for automatic actions update-
• update actions because workflows are complaining about outdated actions

[orbeckst]

Merging PR #508 should trigger initial dependabot runs. Once all of the actions have been updated, we can close this issue.

[orbeckst]

apparently, #509 was all that was needed