Add title function and example of it.

[AtsushiSakai]

No description provided.

[lava]

Nice, thanks for contributing!

Could you explain what you mean by "if PyDECREF, the show function doesn't work on Mac OS"?

[AtsushiSakai]

Hi, lava. matplotlib-cpp is great. I'm looking for like this : )
The comment means that a figure doesn't show on Mac OS if the PyDECREF function is called at the end of "title" function.
Why do you call PyDECREF on the ends of other functhions?

[lava]

All python objects are reference counted, so in your case you are leaking memory by creating three new objects that will never be removed.

It's a pretty small leak though, so if there is some bug on Mac OS that makes this necessary, I'm willing to just leave it. I don't have a Mac to verify it. Would be nice to know why the figure doesnt show, though.

[AtsushiSakai]

OK I understand. yeah, I think the leak is not a problem on practical usage.

[AtsushiSakai]

Thanks for merge 👍