Mono repo -> Master (#22553)

Combines the following repositories into one:

https://github.com/mattermost/mattermost-server
https://github.com/mattermost/mattermost-webapp
https://github.com/mattermost/focalboard
https://github.com/mattermost/mattermost-plugin-playbooks

webapp/Makefile

@@ -0,0 +1,91 @@
+-include config.override.mk
+include config.mk
+
+# The CI environment variable is set automatically in CircleCI and GitLab CI
+CI ?= false
+
+.PHONY: run
+run: node_modules ## Runs app
+	@echo Running Mattermost Web App for development
+
+	npm run run
+
+.PHONY: stop
+stop: ## Stops webpack
+	@echo Stopping changes watching
+
+ifeq ($(OS),Windows_NT)
+	wmic process where "Caption='node.exe' and CommandLine like '%webpack%'" call terminate
+else
+	@pkill -f webpack || true
+endif
+
+.PHONY: restart
+restart: | stop run ## Restarts the app
+
+.PHONY: dev
+dev: node_modules ## Runs app with webpack-dev-server
+	npm run dev-server
+
+.PHONY: test
+test: node_modules ## Runs tests
+	@echo Running jest unit/component testing
+
+	npm run test
+
+.PHONY: check-style
+check-style: node_modules ## Checks JS file for ESLint confirmity
+	@echo Checking for style guide compliance
+
+	npm run check
+
+.PHONY: fix-style
+fix-style: node_modules ## Fix JS file ESLint issues
+	@echo Fixing lint issues to follow style guide
+
+	npm run fix
+
+.PHONY: check-types
+check-types: node_modules ## Checks TS file for TypeScript confirmity
+	@echo Checking for TypeScript compliance
+
+	npm run check-types
+
+.PHONY: build
+build: node_modules ## Builds all web app packages
+	@echo Building Web App and related packages
+
+	npm run build
+
+.PHONY: dist
+dist: build ## Builds all web app packages and copies Boards/Playbooks files into Channels dist folder
+	@echo Packaging Mattermost Web App
+
+	mkdir -p channels/dist/products/boards
+	cp -R boards/dist/* channels/dist/products/boards
+	mkdir -p channels/dist/products/playbooks
+	cp -R playbooks/dist/* channels/dist/products/playbooks
+
+node_modules: package.json $(wildcard package-lock.json)
+	@echo Getting dependencies using npm
+
+ifeq ($(CI),false)
+	npm install
+else
+	# This runs in CI with NODE_ENV=production which skips devDependencies without this flag
+	npm ci --include=dev
+endif
+
+	touch $@
+
+.PHONY: clean
+clean: ## Clears cached; deletes node_modules and dist directories
+	@echo Cleaning Web App
+
+	npm run clean --workspaces --if-present
+	rm -rf node_modules
+
+## Help documentation à la https://marmelab.com/blog/2016/02/29/auto-documented-makefile.html
+.PHONY: help
+help:
+	@grep -E '^[0-9a-zA-Z_-]+:.*?## .*$$' ./Makefile | sort | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-30s\033[0m %s\n", $$1, $$2}'