[fix] pfe-accordion style issues with chevron and interaction states

[starryeyez024]

Description of the issues

• chevron should be thicker
• on disclosure variant, open state, chevron should be nudged upwards to better align with text
• on accordion, the chevron faces the wrong direction
• Focus state should have blue ring
• Hover and active state should change the background color of the header

Impacted component(s)

• pfe-accordion

Steps to reproduce

1. Go to the pfe-accordion demo page: http://localhost:8000/elements/pfe-accordion/demo/
2. Notice that the chevron points down and it should point to the right when closed
3. Expand the accordion
4. Notice that the chevron points up, and it should point down when open

Screenshots

Please refer to design specs and original issue with notes and other theme info