Error before:
```
Warning: validateDOMNesting(...): <div> cannot appear as a descendant of <p>.
at div
at AccessibleButton (webpack-internal:///470:43:7)
at span
at p
at li
at NewRoomIntro (webpack-internal:///2063:77:71)
at ol
at div
at div
at AutoHideScrollbar (webpack-internal:///1020:37:5)
at ScrollPanel (webpack-internal:///1106:69:5)
at ErrorBoundary (webpack-internal:///2070:47:5)
at MessagePanel (webpack-internal:///2060:169:5)
at TimelinePanel (webpack-internal:///2095:113:5)
at div
at div
at div
at MainSplit (webpack-internal:///2019:31:5)
at ErrorBoundary (webpack-internal:///2070:47:5)
at main
at RoomView (webpack-internal:///2018:330:5)
at div
at div
at div
at LoggedInView (webpack-internal:///1907:130:5)
at ErrorBoundary (webpack-internal:///2070:47:5)
at MatrixChat (webpack-internal:///1900:234:5)
```
* Apply `strictNullChecks` to `src/components/views/room_settings/*`
* Restore tsconfig.json
* Conform more code to `strictNullChecks`
* Iterate
* Update matrix-widget-api
* Conform more code to `strictNullChecks`
* add poll history tab to room settings
* test poll history in room settings
* remove posthog tracking for poll his
* remove labs flag for poll history
* i18n
* add poll history tab to room settings
* test poll history in room settings
* remove posthog tracking for poll his
* use consistent label for polls history
* basic sync setup
* formatting
* get loudest value for synced rules
* more types
* test synced rules in notifications settings
* type fixes
* noimplicitany fixes
* remove debug
* tidying
* extract updatePushRuleActions fn to utils
* extract update synced rules
* just synchronise in one place?
* monitor account data changes AND trigger changes sync in notifications form
* lint
* setup LoggedInView test with enough mocks
* test rule syncing in LoggedInView
* strict fixes
* more comments
* one more comment
* add error variant for caption component
* tests for new error message
* tweak styles
* noImplicitAny
* revert out of date prettier changes to unrelated files
* limit inline message to radios only, tests
* strict fix
* Test MessagePanel rendering with hidden events
* Cache the results of shouldShowEvent in MessagePanel
* Combine an event and its shouldShow info into a single object
* basic sync setup
* formatting
* get loudest value for synced rules
* more types
* test synced rules in notifications settings
* type fixes
* noimplicitany fixes
* remove debug
* tidying
* extract updatePushRuleActions fn to utils
* extract update synced rules
* just synchronise in one place?
* monitor account data changes AND trigger changes sync in notifications form
* lint
* setup LoggedInView test with enough mocks
* test rule syncing in LoggedInView
* strict fixes
* more comments
* one more comment
