Add bootstrap accordion block

[ev-sc]

Fixes STW-27

This adds a custom block with a bootstrap accordion template.

• The block takes a text title and RichTextBlock or PersonListBlock as content
• Takes styling from the site theme

Screencast.from.2023-02-09.10-32-24.webm

[linear]

STW-27 Add an accordion feature to page elements

could we add accordion feature to page elements (ie: text, cta, person listing, organisation listing, alert) as a default? it'll allow for a web user to shorten a webpage to the bits they want to see.
example of a page that would benefit from this: https://www.stop-watch.org/what-we-do/projects/girls-women-project/

Originally posted by HabKadSW in https://github.com/commonknowledge/stopwatch/issues/35#issuecomment-1237075612

[janbaykara]

LGTM