feat: allow dropdowns in basic header

[CallumNZ]

Proposed Changes

Reference: https://github.com/GeoNet/tickets/issues/11365

Changes proposed in this pull request:

• allow dropdowns in basic header

Production Changes

The following production changes are required to deploy these changes:

• None

Review

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• This is a content (documentation, web page etc) only change.
• This is a minor change (meta data, bug fix, improve test coverage etc).
• This is a larger change (new feature, significant refactoring etc). Please use the code review guidelines to add a checklist below to guide the code reviewer.

Code Review Guide

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[bpeng]

OK