Mac OS launchctl config

This isn't so much an issue as something that I wanted to share for the benefit of others.

I set up Cavalcade for a local site (which is powered by [Valet+](https://github.com/weprovide/valet-plus)), and I wanted to have Cavalcade automatically launch using the native Mac OS `launchctl` system.

Here's the config file I ended up using, with specifics replaced:

```xml

Label
some-site.cavalcade

ProgramArguments

bash
-lc


~/projects/Cavalcade-Runner/bin/cavalcade /path/to/wp/site

RunAtLoad

StandardOutPath
/usr/local/var/log/cavalcade.log

StandardErrorPath
/usr/local/var/log/cavalcade_error.log

```

This file is placed into my `~/Library/LaunchAgents/` directory with a `.plist` extension. For consistency, I've matched the file name with the Label `some-site.cavalcade` above. To load get this running, I then do this:

```
launchctl load -w ~/Library/LaunchAgents/some-site.cavalcade.plist
```

Review the macOS launchctl plist and launchctl load command included in the issue, then inspect the repository's existing documentation for the appropriate place to describe local Cavalcade setup. Done should mean the configuration and loading steps are documented accurately for a local site.

Written by the indexing model from the issue text.