Clarify default functionality

Problem/Motivation

Steps to reproduce

Like it was mentioned earlier in another issue the expand-collapse behavior described on the module page is not provided by this module.

In case of the previous issue, it was mentioned that the Bootstrap theme will be added as a dependency, so together they work. But since then, the Bootstrap dependency was removed(?)

Proposed resolution

Update the module page with actual information on what the module provides out of the box and how it can be used.

Remaining tasks

Update the project page.

User interface changes

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API changes

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Data model changes

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