Description

This PR makes the ItemCollectionMapperComponent and CollectionItemMapperComponent themeable by default,

Instructions for Reviewers

Enable the "custom" theme and for both components, make some modifications to the component in the custom theme that are obvious.

The ItemCollectionMapperComponent is visible at: Edit Item -> Collection Mapper
The CollectionItemMapperComponent is visible at: Edit Collection -> Item Mapper

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Checklist

• My PR is created against the main branch of code (unless it is a backport or is fixing an issue specific to an older branch).
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