Also include bootstrap.js to make collapsing actually work, and change
order of links in head to ensure js is included in the 'correct' order

Is it less monolithic? Yes
Is it actually any better? Uhh

This is still doing some reasonably code-smelly things which could
probably be improved with a decent JavaScript templating engine, but:

- it's after 10PM on a SAturday night and I've been working on this all
  afternoon
- it works for now
- I don't want to go too far down the rabbit hole of super-polished code
  (hah!) before I check that the output format suits C

It is actually better in the sens that we present charts first (easier
to see at a glance) with their data below them.

Todo:
 - sort output of outcomesBalance for chart (already sorted for table)
 - hide/show toggles
 - make the doughnut chart more straightforward (swap legend order,
   rename labels)

This is still pretty quick and dirty, with lots of refactoring and
general tidying up ahead; but it gives an example structure to start
from

Emphasis on the dirty, not so much 'quick' ! This shows select outputs
from the default Asphodice class:
 - rerolls
 - outcome balance
 - outcomes

This information is presented in a Bootstrap card:

https://getbootstrap.com/docs/5.0/components/card/

Can now build all with 'gulp' (if gulp-cli installed)

Big commit. Breakdown:
 - .gitignore includes gulpfile.js (otehrwise excluded)
 - gulpfile sets up build steps + browsersync
 - src/ files for FE (stub for now)
 - moved ts to src/ for consistency
 - update tsconfig with new paths
 - package.json lists new reqs