Update to Bootstrap ≥5.3.1

[KCarlile]

Background

Flash Chord is running on Bootstrap 4.5 right now and ≥5.3.1 is out, so we should update to the latest version. This will require updates to CSS (at least the collapse/expand. of the changelog on the about page).

Acceptance Criteria

• Flash Chord is running on the latest version of Twitter Bootstrap

Approach

• Update the includes to ≥5.3.1
• Test visual layout
• Test any functionality, specifically the expand/collapse of the changelog on the About page

Notes

...