#119: Document location of entry point method.

[yringler]

This is something that confused me when I was working on using this plugin. Perhaps some additional documentation will help someone else.

Related to #119.

[hacker1024]

This happened to me, too. From memory, it is documented somewhere, but I can't remember where.

It can be a static class member, though - you should probably update your documentation to mention that.

When you think about it, it makes complete sense - isolates cannot access each-other's memory, so it's impossible for an isolate to call another's object's function.

[ryanheise]

Yay, I finally got around to this one :-) @yringler I'm sorry it took me so long to get around to this, and if it hadn't taken me so long, I might have been able to merge your PR before I ended up incidentally duplicating your work months later.

@hacker1024 , I checked for the first time whether static class members truly work (as per the Flutter documentation), and it seems they don't, despite the Flutter documentation claiming they do (unless I'm misunderstanding the documentation). When I tried, I got this error in the logs: "NoSuchMethodError: No top-level getter '_audioPlayerTaskEntrypoint' declared." which sounds pretty definitive. It's expecting a top-level function. Accordingly, I've updated the plugin documentation, README, FAQ, and also added comments in the example to just say that it should be a top-level function.

[yringler]

Great!