report root assertions with ✘ and ✔

[robstoll]

Platform (jvm, js, android): all Extension (none, kotlin 1.3, jdk8): none

Code related feature

Based on the discussion in https://github.com/robstoll/atrium-roadmap/issues/55

To emphasise that we only report failed assertions per default we want to change the root bullet points accordingly to ✘ and ✔ (where only ✘ are shown per default).

Following the things you need to do:

lib

• [ ] TextFallbackAssertionFormatter needs to report like TextSummaryAssertionGroupFormatter