*  (typescript) fixing strictNullChecks=true issues

* Patch test-helpers

* Strict patch

* ESLint no-default-exports 12 - All loot-core folders except server

* Release notes

* Fix imports

* Add "end" field with date/count options

* Use "end" field to generate schedule

* Show "end" field in recurring description

* Disable weekend before/after picker when not enabled

* Add release notes

* Fix failing typechecks

* Add some description tests

* PR feedback

* 'Features', not 'Feature'

* Fix goal templates infinite loop

* Empty commit to bump ci

* Fix bug where schedule templates in the past would apply incorrectly

For example, if you had a schedule which started in November 2023 for
1.00, and you applied the schedule in October 2023, then you would end
up with a value of 0.50 applied in October.

* Fix handling of schedules with an end date

This commit also includes a refactor of the skip-weekend logic: rather
than referring only to dates with skipped weekends (which requires
checking whether the "next date" request worked correctly), we track a
"base date" which is the previous value of the schedule according to the
rrule, excluding any weekend-skipping. This lets us use `addDays(baseDate, 1)`
to get the next occurrence, regardless of the weekend behaviour.

Doing things this way ensures that the loop will always make progress.

* Only compute skipped weekend if weekend skips were requested

* Fix typo in iterate-schedule-occurrences code

We should be using `nextBaseDate` to derive the next base date, not
`nextDate`; this is because we want the base date to be guaranteed to
make progress in each loop iteration, so we can finish in at most 30
iterations without duplicate base dates.

* Use const

* Revert const -> let for one mutable variable

* Part 2 of eslint prefer-const

* Release notes

* Update

Another batch of `loot-core` migrated.

Part 1 of the conversion. Mostly renaming js to ts and making sure
things make still sense. Added also handy TS ESLint rules.

In order to support the various .web/.electron/... I ended up adopting
`index.d.ts` as pattern to share type definition. Let me know if that
makes sense for you too. Right now the function type definition is
duplicated, but the solution will be importing from `index.d.ts` and
using `const fn: FnDef = () => ...` that way we can keep all variants in
sync from a single type file.

Such rewrite however is better done in another PR otherwise we risk
confusing git and loosing history (rename + too many changes). Another
thing that might do in the next PR is convert all files to ESModules, as
things get confusing between CJS exports, ESM default/named and TS adds
extra complains.

*  (prettier) adding trailing commas

* More commas