How to specify path to ssh agent socket

### Expected behavior

When building with Docker and ssh agent forwarding, I want to specify the ssh agent path using e.g. the `$HOME` variable or the `~` symbol for the home folder.

### Actual behavior

When specifying the build:docker:ssh string in skaffold.yaml, it seems that one needs to supply the absolute path to the agent socket file.

### Information

- Skaffold version: v2.8.0
- Operating system: Mac 13.4.1
- Installed via: Homebrew

### Steps to reproduce the behavior

Not possible if you do not use the 1Passwort ssh agent. That agent has a separate socket file which needs to be specified.