samples for CharSequence.toContain.atMost

[robstoll]

Code related feature

Following the things you need to do:

api-fluent

• add a atMost method in CharSequenceToContainCheckerSamples
• link in the KDoc of the corresponding function in charSequenceToContainCheckers.kt to the sample via @sample (see atleast)

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[Nikos-Tsiougranas]

I will work on this!