Replace all font styling with global font classes

[SodaVolcano]

Basic Information

Replace all font styling with the styling classes defined in #42 once it's merged for consistency (very fun chore)

[github-actions]

Branch issue-65-Replace_all_font_styling_with_global_font_classes created!

[SeiKasahara]

Should this be a last check that ensuring every pages use the global font classes?

[SodaVolcano]

Not sure what you mean by last check?

All PRs from this point should use the global font classes, any that don't use the style should be corrected during code review so, changes made for this issue can be merged in a PR.