fix: Assorted Typing Fixes (#3348)

With all the commits below, we resolve all outstanding typing issues in the repo, and CI jobs run green.

* fix: Convert DashboardPage and DashboardWidget to TypeScript

* fix: fix type errors in package manager ext

* fix: Convert Post component to TypeScript

* fix: avatar typings should accept null user

* fix: convert Notification component to TypeScript

* fix: properly use `typeof` in ForumApplication

* feat: make Notification content attr generic

* chore: format Notification component

* fix: Convert DiscussionRenamedNotification to TypeScript

* fix(pusher) move shims to a location where they get applied

* fix(pusher): fix some typing errors

* fix(akismet): fix some typing issues

* chore: update core dist typings

* chore(pusher): format

* fix: anchorScroll should accept string selectors

* fix: more accurately represent ApiQueryParamsPlural

* fix: convert PostStreamState to TypeScript

* chore(core): rebuild typings

* feat: allow extending app.routes

* fix: more flexible typings for highlight.ts

* fix: use primitive `number` type for Discussion typings

* fix: convert DiscussionListItem to TypeScript

* chore: rebuild core typings

* fix: final pusher type fixes

* feat: start tags TypeScript conversion

* fix: require-dev tags in pusher for CI TypeScript purposes.

* chore(core): format

* chore(tags): build dist typings

* feat(pusher): use dist types from tags.

* feat: convert flags to TypeScript

* chore(flags): generate dist typings

* fix(akismet): last type errors

* chore: update .yarn-integrity

* chore: partially run flarum-cli audit infra --fix

The tsconfig changes from that command are ignored, since we don't yet support "replacable sections" that would let us add custom config.

* chore: use type imports

* fix: broader gitattributes

* chore: run flarum-cli audit infra --monorepo --fix

* feat: make `app.data` typings extensible

* chore(core): format

* chore: boost tags TypeScript coverage

* fix(tags): further increase type coverage.

js-packages/tsconfig/.gitattributes

@@ -1,16 +0,0 @@
-.gitattributes export-ignore
-.gitignore export-ignore
-.gitmodules export-ignore
-.github export-ignore
-.travis export-ignore
-.travis.yml export-ignore
-.editorconfig export-ignore
-.styleci.yml export-ignore
-
-phpunit.xml export-ignore
-tests export-ignore
-
-js/dist/* -diff
-js/dist/* linguist-generated
-
-* text=auto eol=lf

js-packages/webpack-config/.gitattributes

@@ -1,3 +0,0 @@
-# https://yarnpkg.com/getting-started/qa#which-files-should-be-gitignored
-/.yarn/releases/** binary
-/.yarn/plugins/** binary