Remove style components from PageHeader component

[joshsadam]

Description of changes

Starting to use CSS variables now that they are available in all major browsers. This allows us to start using theme and remove the kind of tacky colours.js file.

Related issue

N/A

Checklist

Things for the developer to confirm they've done before the PR should be accepted:

• CHANGELOG.md (and UPGRADING.md if necessary) updated with information for new change.
• Tests added (or description of how to test) for any new features.
• User documentation updated for UI or technical changes.

[deepsidhu85]

This looks good and I'm glad we can use the css variables now. Just one comment but I'm open to leaving it the way it is. Can we put the css files in a css directory within the components? Just to keep the style files separate from the component files

[deepsidhu85]

This looks good and I'm glad we can use the css variables now. Just one comment but I'm open to leaving it the way it is. Can we put the css files in a css directory within the components? Just to keep the style files separate from the component files

As per our discussion this is how we want to organize it so no changes need to be made