add password-manager-service interface

[nathanclairmonte]

Rationale

Two users (Ant and David) have been experiencing the following error when running GHT:

✖ Error replicating job post: Error: Failed to launch the browser process!
error: error running snapctl: snap "ght" has no plug or slot named "password-manager-service"
[0218/165827.385912:ERROR:chrome_main.cc(202)] Multiple targets are not supported in headless mode.


TROUBLESHOOTING: https://pptr.dev/troubleshooting

Jon Seager has suggested it could be due to a non-standard wallet/keyring implementation on their machines, and has suggested that we add the password-manager-service as an interface in the snapcraft.yaml, create a PR, and get either Ant or David to build from source on that branch, run a command to connect the interface (sudo snap connect ght:password-manager-service), and try again. This is that PR.

Done

• Added password-manager-service to the snapcraft.yaml