feat: Add brand specific assets

[coire1]

Description

This PR introduces the ThemeExtension BrandAssets that allows to have assets that are specific for brand.
A specific use case for that is related to logos: in this way when a brand is switched and the related Theme is loaded also the logo can be updated accordingly. This approach can be used for every brand specific asset in the application.

Related Issue(s)

Closes #497

Please confirm the following checks

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream module

[github-actions]

❌ Test Report | ${\color{lightgreen}Pass: 97/99}$ | ${\color{red}Fail: 2/99}$ |