Add MySQL example.

[Potherca]

I thought it might be useful to have a working example for MySQL, in case folks want/need to use a different version from the installed default.

I've tried to make the code look similar to already existing examples.

The example can be seen working here: https://github.com/potherca-contrib/example-services/actions/runs/449593636

If you have any feedback, please let me know! :+1:

[Potherca]

@jrfnl I'd be curious to know why job.services.<service id>.ports did not work... but other than that, I am very much inclined to include your edit. :+1:

Maybe @andymckay or @chrispat could comment on this?

[jrfnl]

@Potherca I honestly wouldn't know. I also found that using 127.0.0.1 (or in practice: 127.0.0.1:3306) worked better than using localhost. But to be honest, I tried so much that it is hard to say which bit was the bit which fixed it.

In the end, the changes I needed for this particular workflow were quite small, but the complete combi was needed to get it all working. Relevant commits:

• https://github.com/WordPress/wordpress-importer/pull/93/commits/122fdc26c07215d4fcfb30a9e91037e3e5c4cea4
• https://github.com/WordPress/wordpress-importer/pull/93/commits/5bc6b88bd122847211e903ba8caef2bd84d0705a