Added 'Save all chart images' button to School and Trust cost comparison pages

[WolfyUK]

Context

AB#246636 AB#242099

Change proposed in this pull request

• Added <ShareContentByElements /> component for use with any HTMLElement that generates .pngs for each matching element and bundles them into a .zip which is then sent to the client
• Added default implementation to be to select by matching element class name(s), which may be outside the React context
• Added optional progress indicator to <ShareContentByElements /> component
• Added 'save all' button to School and Trust comparison pages
• Ensured if 'table' mode selected in chart radios then first select 'chart' before saving chart images

Guidance to review

Multiple image save feature may be demoed in the vite dev server. To view in the web app, build front-end-components and copy to Web before visiting the affected pages. Seems to be performant even on the largest Trust, but it is anticipated that a future design crit may raise additional work, especially:

• around the 'progress' indicator that provides additional context to the user during the potentially long-running task
• visibility/disabled state/location of the button

Checklist (add/remove as appropriate)

• Work items have been linked (use AB#)
• Your code builds clean without any errors or warnings
• You have run all unit/integration tests and they pass
• Your branch has been rebased onto main
• You have tested by running locally
• You have reviewed with UX/Design