New Editorial Practice: If a characteristic of an example pattern implementation is optional, document optionality with link to pattern

[mcking65]

Questions and confusion can arise when the example implementation of a design pattern implements an optional behavior or characteristic and the documentation of that behavior or characteristic on the example page does not inform readers that it is optional. For example, see #1318.

Develop an editorial convention for highlighting optional or recommended aspects of examples. consider providing a link to the design pattern at the point where the behavior or characteristic is documented on the example page.

Propose a convention in a PR to address #1318.