Fix lilyplay example

[JeffFessler]

The existing lilyplay example would not run due to an apparently obsolete reference to maxoutchans.
This PR fixes that and adds a brief comment to explain what the file does.

[codecov]

Codecov Report

Merging #106 (d702d4e) into master (f6cd300) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #106   +/-   ##
=======================================
  Coverage   97.66%   97.66%           
=======================================
  Files           2        2           
  Lines         342      342           
=======================================
  Hits          334      334           
  Misses          8        8           

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[JeffFessler]

Can be closed in favor of the more comprehensive #107.
I don't have any experience with Makie so I won't be any help there, sorry!

[JeffFessler]

BTW, the default tests include 1.4 and 1.5 (in many OS flavors). Now that 1.6 is the LTS we could save some carbon footprint by just testing (say) 1.3, 1.6, 1 and nightly if you want.