docs: update docs to reflect updated usages and env variables

docs/usage/distrobox-create.md

@@ -16,15 +16,17 @@ Usage:
 	distrobox create --image alpine:latest --name test --init-hooks "touch /var/tmp/test1 && touch /var/tmp/test2"
 	distrobox create -i docker.io/almalinux/8-init --init --name test --pre-init-hooks "dnf config-manager --enable powertools && dnf -y install epel-release" 
 
-You can also use environment variables to specify container name and image
+You can also use environment variables to specify container name, image and container manager:
 
-	DBX_NON_INTERACTIVE=1 DBX_CONTAINER_NAME=test-alpine DBX_CONTAINER_IMAGE=alpine distrobox-create
+	DBX_CONTAINER_MANAGER="docker" DBX_NON_INTERACTIVE=1 DBX_CONTAINER_NAME=test-alpine DBX_CONTAINER_IMAGE=alpine distrobox-create
 
 Supported environment variables:
 
-	DBX_NON_INTERACTIVE
-	DBX_CONTAINER_NAME
+	DBX_CONTAINER_CUSTOM_HOME
 	DBX_CONTAINER_IMAGE
+	DBX_CONTAINER_MANAGER
+	DBX_CONTAINER_NAME
+	DBX_NON_INTERACTIVE
 
 Options:
 

docs/usage/distrobox-enter.md

@@ -15,9 +15,14 @@ Usage:
 	distrobox-enter --additional-flags "--env MY_VAR=value" --name test -- bash -l
 	MY_VAR=value distrobox-enter --additional-flags "--preserve-fds" --name test -- bash -l
 
+You can also use environment variables to specify container manager and container name:
+
+	DBX_CONTAINER_MANAGER="docker" DBX_CONTAINER_NAME=test-alpine distrobox-enter
+
 Supported environment variables:
 
 	DBX_CONTAINER_NAME
+	DBX_CONTAINER_MANAGER
 
 Options:
 

docs/usage/distrobox-list.md

@@ -8,6 +8,14 @@ Usage:
 
 	distrobox-list
 
+You can also use environment variables to specify container manager
+
+	DBX_CONTAINER_MANAGER="docker" distrobox-list
+
+Supported environment variables:
+
+	DBX_CONTAINER_MANAGER
+
 Options:
 
 	--help/-h:		show this message

docs/usage/distrobox-rm.md

@@ -8,6 +8,16 @@ Usage:
 	distrobox-rm --name container-name [--force]
 	distrobox-rm container-name [-f]
 
+You can also use environment variables to specify container manager and name:
+
+	DBX_CONTAINER_MANAGER="docker" DBX_CONTAINER_NAME=test-alpine distrobox-rm
+
+Supported environment variables:
+
+	DBX_CONTAINER_MANAGER
+	DBX_CONTAINER_NAME
+	DBX_NON_INTERACTIVE
+
 Options:
 
 	--name/-n:		name for the distrobox

docs/usage/distrobox-stop.md

@@ -11,6 +11,16 @@ Usage:
 	distrobox-stop --name container-name
 	distrobox-stop container-name
 
+You can also use environment variables to specify container manager and name:
+
+	DBX_CONTAINER_MANAGER="docker" DBX_CONTAINER_NAME=test-alpine distrobox-stop
+
+Supported environment variables:
+
+	DBX_CONTAINER_MANAGER
+	DBX_CONTAINER_NAME
+	DBX_NON_INTERACTIVE
+
 Options:
 
 	--name/-n:		name for the distrobox