Update type scale

[anandamaryon1]

Description

This PR brings together two related typography proposals:

• change large heading size from 32px to 36px: Add 36 to type scale and swap headings to use it #989
• change heading medium size for better contrast with heading small: Improve the hierarchy of H3 and H4 heading styles nhsuk-service-manual-community-backlog#445.

Alongside these changes, it:

• adjusts the heading line-heights for better consistency
• reduces the heading captions sizes for more contrast with headings
• adds table caption size classes to allow table captions to be sized similar to headings
• tweaks print styles for typography, to reduce heading sizes, and slightly reduce the font size, whilst maintaining Clear Print size, for more efficient use of paper and better overall readability

Checklist

• Tested against our testing policy (Resolution, Browser & Accessibility)
• Follows our coding standards and style guide
• CHANGELOG entry