Update ssh-agent setup for 1Password in zshrc

[neiromaster]

License Acceptance

• This repository is Apache version 2.0 licensed (some scripts may have alternate licensing inline in their code) and by making this PR, I am contributing my changes to the repository under the terms of the Apache 2 license.

Description

The function load-our-ssh-keys in zshrc has been updated to check for the existence of 1Password before setting up the ssh-agent. Now, the ssh-agent will only be initialized for 1Password if it's installed on the system. This change effectively prevents potential errors when 1Password is not available. Fixes #292

Type of changes

• A helper script
• A link to an external resource like a blog post or video
• Text cleanups/updates
• Test updates
• Bug fix
• New feature
• Plugin list change

Checklist

• I have read the CONTRIBUTING document.
• I have updated the readme if this PR changes/updates quickstart functionality.
• All new and existing tests pass.
• Any scripts added use #!/usr/bin/env interpreter instead of potentially platform-specific direct paths (#!/bin/sh is an allowed exception)
• Scripts are marked executable
• Scripts do not have a language file extension unless they are meant to be sourced and not run standalone. No one should have to know if a script was written in bash, python, ruby or whatever. Not including file extensions makes it easier to rewrite the script in another language later without having to change every reference to the previous version.
• I have added a credit line to README.md for the script
• If there was no author credit in a script added in this PR, I have added one.
• I have confirmed that the link(s) in my PR are valid.

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[dglynn]

An if check here, makes sense too. 👍

[unixorn]

Nice catch, thank you!