* allow service classes to define a static example
* define static example for some services
(apm, appveyor, cdnjs, clojars, gem, librariesio, npm, uptimerobot)
* add/update tests
This allows us to show an example without making an API call to a live service for better performance.
We can now specify 3 fields in the example definition:
* urlPattern for the version with placeholders e.g: /npm/dw/:package.svg
* ExampleUrl/Uri for the concrete example e.g: /npm/dw/localeval.svg
* PreviewUrl/Uri for the static (or live) image we will actually show
