chore(docker): update Makefile and Readme (#511)

Makefile

@@ -145,9 +145,9 @@ all_pkgs: cross_build cross_build_for_rpm
 
 .PHONY: docker
 docker:
-	docker build --no-cache -t $(TARGET):$(VERSION) -f deploy/docker/Dockerfile .
-	docker build --no-cache -t $(TARGET):$(VERSION)-slim -f deploy/docker/Dockerfile-slim .
-	docker build --no-cache -t $(TARGET):$(VERSION)-alpine -f deploy/docker/Dockerfile-alpine .
+	docker buildx build --no-cache --platform=linux/amd64 -t $(TARGET):$(VERSION) -f deploy/docker/Dockerfile . --load
+	docker buildx build --no-cache --platform=linux/amd64 -t $(TARGET):$(VERSION)-slim -f deploy/docker/Dockerfile-slim . --load
+	docker buildx build --no-cache --platform=linux/amd64 -t $(TARGET):$(VERSION)-alpine -f deploy/docker/Dockerfile-alpine . --load
 
 .PHONY:cross_docker
 cross_docker: cross_prepare

deploy/docker/README.md

@@ -160,7 +160,7 @@ When modifying configuration files through environment variables, the environmen
 ```
 KUIBER__BASIC__DEBUG => basic.debug in etc/kuiper.yaml
 
-MQTT_SOURCES__DEMO_CONF__QOS => demo_conf.qos in etc/mqtt_source.yaml
+MQTT_SOURCE__DEMO_CONF__QOS => demo_conf.qos in etc/mqtt_source.yaml
 ```
 
 The environment variables are separated by two "_", the content of the first part after the separation matches the file name of the configuration file, and the remaining content matches the different levels of the configuration item.