Fix Shopify banner css

[ricardobrg]

Issue description from https://github.com/tiki/tiki-sdk-js/issues/74

TIKI SDK JS relies on using the rem unit for sizing, which can lead to unexpected behavior when the HTML root element has a custom font size instead of the default browser size of 16px. This is particularly noticeable in pages like the Shopify standard theme, where the base font size is set to 10px, causing font sizes in the TIKI UI to appear smaller than intended.

To address this issue, we need to update the TIKI SDK JS UIs to use a base font size of 16px instead of relying on the rem unit for sizing. This will ensure consistent and expected font sizes across different environments and themes. 

This task is to solve this locally in the Shopify app, so we are not on hold from the definitive solution in TIKI SDK JS

Tasks:

• [x] Overwrite the TIKI SDK JS CSS to fix the font sizing in the Shopify app.

[ricardobrg]

check with 2.1.0

[ricardobrg]

working in JS 2.1.1