Support to install atest as a macOS service

[LinuxSuRen]

We already support it on the Linux platform. See also here.

Please feel free to read the following references below if you're interested in this issue:

• About Daemons and Services

[LinuxSuRen]

I found an article which is about this. And a sample service file like below:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>Label</key>
    <string>com.github.linuxsuren.atest</string>
    <key>ServiceDescription</key>
    <string>API Testing Server</string>
    <key>ProgramArguments</key>
    <array>
        <string>/usr/local/bin/atest</string>
        <string>server</string>
    </array>
    <key>RunAtLoad</key>
    <false/>
</dict>
</plist>
<!-- 
sudo cp sample/com.github.linuxsuren.atest.plist /Library/LaunchDaemons
sudo launchctl unload /Library/LaunchDaemons/com.github.linuxsuren.atest.plist
sudo launchctl load /Library/LaunchDaemons/com.github.linuxsuren.atest.plist
sudo launchctl start com.github.linuxsuren.atest
sudo launchctl list | grep atest
-->