add samples for featureAssertions of api-fluent

[robstoll]

Code related feature

See for the initial request: #624

With this issue we want to add samples for featureAssertions.kt of api-fluent

Following the things you need to do:

api-fluent

• create FeatureExtractorSamples in apis/fluent-en_GB/atrium-api-fluent-en_GB-common/src/test/kotlin/ch/tutteli/atrium/api/fluent/en_GB/samples
  • add one function per function in featureAssertions.kt (see AnyExpectationSamples)
  • refer to the sample in the KDoc of the corresponding function in featureAssertions via @sample (check out toEqual in anyExpectations.kt to see how you have to refer to the sample)

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[iljakorneckis]

I'll work on this, @robstoll Looks a bit more involved than the other sample tasks, so I'll try to have something up for review soon. The README has examples, so I'll also use that.