Description of problem:

When using a home page markdown card with different heading levels (# vs ## vs ###) they all look really similar.

The theme uses the font sizes that looks to similar (or are the same), so these need to be updated.

The font sizes should be aligned with PatternFly (5) for now: https://v5-archive.patternfly.org/design-foundations/typography

Steps to Reproduce

1. Customize the home page with a markdown card

Actual results:

Different heading levels looks really similar (or are the same)

Expected results:

Different heading levels should have different font sizes

Reproducibility (Always/Intermittent/Only Once):

Always

Build Details:

1.4 I guess

Additional info (Such as Logs, Screenshots, etc):

rh-ee-bwilcock slack thread on that: https://redhat-internal.slack.com/archives/C05HGAR2DT5/p1736952052849679?thread_ts=1736776745.790339&cid=C05HGAR2DT5