fix: in cgAdd: make cgLayer be optional

[nytamin]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  quality of life improvement

• What is the current behavior? (You can also link to an open issue here)

cgAdd requires the parameters cgLayer and playOnLoad

• What is the new behavior (if this is a feature change)?

cgLayer is optional and defaults to 1

playOnLoad is optional and defaults to true

• Other information:

In my experience, cgLayer and playOnLoad are rarely used nowadays, so I think that we should allow for leaving them out and fill in the most-commonly used values.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (278eb2b) 82.03% compared to head (3066ee3) 82.16%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #182      +/-   ##
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+ Coverage   82.03%   82.16%   +0.13%     
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  Files          14       14              
  Lines         729      729              
  Branches      140      166      +26     
==========================================
+ Hits          598      599       +1     
+ Misses        130      129       -1     
  Partials        1        1              

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[mint-dewit]

In my experience, cgLayer and playOnLoad are rarely used nowadays

I don't know if we as library maintainers are allowed to make such assumptions. Loading a template before playing it certainly does not seem like such a crazy idea.

I'm definitely not against it, it would be useful for most of what I do too but it feels like a dangerous decision to make.

[Julusian]

cgLayer is definitely falling out of use, as it has no effect when using html.
playOnLoad though is still relevant, but as maintainers of the library we can make decisions on what we think are sane defaults. users are still able to overrule those decisions by supplying a value.

I think I do agree that maybe it would be better for playOnLoad to default to false. This method is called cgAdd and there is a separate cgPlay method, so I think it will be more commonly expected for cgAdd to not autoplay

[nytamin]

Good points!
I've revised this PR to only modify the cgLayer to be optional.
After reading your comments, I changed my mind regarding the playOnLoad property, lets keep it mandatory to reduce risk of unexpected behaviour for new users of the library.