Allow to customize Headline Sizes

[tvdeyen]

What is this pull request for?

Pass a multi dimensional array instead of numbers and Alchemy will use this for the select tag

Checklist

• [x] I have followed Pull Request guidelines
• [x] I have added a detailed description into each commit message
• [x] I have added tests to cover this change

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.86%. Comparing base (5f1790c) to head (c03285b).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2843 +/- ## ======================================= Coverage 95.86% 95.86% ======================================= Files 229 229 Lines 6208 6211 +3 ======================================= + Hits 5951 5954 +3 Misses 257 257 ```

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