Refactor css
Refactors the CSS and reorders and renames the HTML where necessary.
Including:
- Structured CSS in a way where we can pull out general styles from component styles
- Removed any unnecessary CSS
- Scales according to font size on body (with two breakpoints to keep sensible line length)
- Relying on Bulma styles wherever possible
- Using BEM naming conventions for component customisation on top of Bulma naming conventions
Will still need reviewing for accessibility in the future to keep an eye on:
- Source order: whether source order reflects focus order
- Semantic use of tabs: currently active tabs are only shown in a visual manner. Current tabs should probably also be headings