Add search bar for large Activity lists

[kittsville]

As a user with a lot of activities I would like a search bar So I don't have to scroll to find the activity I would like to select

• The search bar should only appear if the list is long
• The search bar should search both activity titles and their items

[kittsville]

This doesn't play nicely with checklist generation, as Activities hidden by the current search term still end up in the generated checklist. If they're not included I'd also need to stop displaying "Generate Checklist" if the search term hides all selected Activities. The two have to be coupled so I'll have a think of the least nasty way to do so

[kittsville]

I just realised the search bar stopped showing up

[kittsville]

Turns out I never committed the file from the ubuntu machine, yay for deployments not happening automatically from source and uncomitted code being able to end up in prod. Will need to check on the ubuntu machine if search.js is still there otherwise I'll have to remake it based on Recibase or whichever latest version of the search script I used. Really I need make it a generic library that they all share rather than copying it every time