Add frontend local dev script for Clickhouse development

[alexkim205]

Changes

When I want to make frontend changes with Clickhouse, hot reloading doesn't work quite as you expect it to when running the frontend in a docker image. For every frontend change, the frontend app reloads 10-11 times so you have to wait 1-2min for every reload which makes for a suboptimal dx.

Let's make a equivalent docker-backend.sh script for Clickhouse, so that devs can spin up a local React application that can talk to a dockerized backend. I also added a one-liner script in package.json that you can run to get a dockerized backend and local frontend up and running in no time.

Also requires doc updates in this PR

Steps

1. yarn start-ch-dev

To quit everything

1. Ctrl/Cmd+C

docker compose -f ee/docker-compose.ch.yml down
DEBUG=1;DJANGO_SETTINGS_MODULE=posthog.settings;PRIMARY_DB=clickhouse;CLICKHOUSE_HOST=clickhouse;CLICKHOUSE_DATABASE=posthog;CLICKHOUSE_SECURE=false;CLICKHOUSE_VERIFY=false python migrate.py migrate_clickhouse

[alexkim205]

Merging this because there is no impact with a few more dev scripts ;). Also need this for my PR's and it's getting painful to git stash all the time