Remove jquery

[timwis]

Nearly finished, but not quite — just pushing this up as a draft for visibility.

Still need to:

• [x] Get components/dataset-display.js working
• [x] Pull in the minimal JS needed for bootstrap components like the nav bar

Note that it will be worth comparing bundle sizes before merging, to verify whether this PR adds value (tree shaking has come a long way)

[timwis]

Bundle size comparison

• Current (with jquery): 170.11 KB
• With jQuery and default bootstrap js removed: 106.43 KB

We could shave off another large chunk (probably 60 KB) by getting tree shaking working with lodash, but it's not immediately possible because of the use of the library's chain method (which pulls in the whole library, as I understand it), so would require a refactor in two of the components.

Last thing I want to do on this branch is just check the browser support to make sure we're comfortable with the changes.

[BryanQuigley]

Was looking to review this, but it looks like bootstrap 5 dropped JQuery anyway. Does this mean we would just stick on bootstrap instead of bootstrap.native?

[timwis]

Yep, that's right. To be honest, I got to the end of this pull request and just felt like it made readability worse without much benefit. Happy to carry on with it once we've got bootstrap 5 ready, though I'm half-tempted to just rewrite it (perhaps in stimulus, which takes a similar multi-page app approach) since it's so little JS at this point.