Update heading styles for the Springer brand-context

[foxintherain]

What

Update the heading styles to ensure a clear visual hierarchy that can be used consistently across all springer sites.

Why

@Heydon has discovered from working on the new springer.com landing pages that heading styles are being overridden on the journal sites. This is due to H2's and H1's not having a lot of visual difference.

Done when

• [x] New heading styles are agreed with UX from SPA team (@foxintherain)
• [x] Update styles in toolkit (@Heydon)
• [x] Communicate updates to Pandora team (@foxintherain)

[foxintherain]

New typography scale:

[amyhupe]

@heydon - have assigned this to you as we think this should now be ready to update in the toolkit.

[foxintherain]

Updated following chat with @Heydon

[foxintherain]

Final update:

[Heydon]

@amyhupe @foxintherain see https://github.com/springernature/frontend-toolkits/pull/727 for the toolkits changes

[foxintherain]

@matteo-gildone @benjclark @ricky-lau Please toolkit changes https://github.com/springernature/frontend-toolkits/pull/727

[foxintherain]

FYI @tesstesstess