Update readme and add Makefile

Makefile

@@ -0,0 +1,23 @@
+.PHONY: clean list-images build publish
+
+IMAGE_NAME ?= wpengine/site-deploy
+MAJOR_VERSION ?= 1
+MINOR_VERSION ?= 0
+PATCH_VERSION ?= 0
+TAG ?= latest
+IMAGE := $(IMAGE_NAME):$(TAG)
+
+clean:
+	$(eval CURRENT_IMAGES=`docker images $(IMAGE_NAME) -a -q | uniq`)
+	docker rmi -f $(CURRENT_IMAGES)
+
+list-images:
+	docker images $(IMAGE_NAME) -a
+
+build:
+	docker build --no-cache -t $(IMAGE) ./
+
+version: build
+	docker image tag $(IMAGE) $(IMAGE_NAME):v$(MAJOR_VERSION) && \
+	docker image tag $(IMAGE) $(IMAGE_NAME):v$(MAJOR_VERSION).$(MINOR_VERSION) && \
+	docker image tag $(IMAGE) $(IMAGE_NAME):v$(MAJOR_VERSION).$(MINOR_VERSION).$(PATCH_VERSION)

README.md

@@ -1,2 +1,47 @@
-# site-deploy
+# wpengine/site-deploy
 Base image to build VCS integrations enabling customers to deploy their site to WP Engine
+
+## How to Build
+
+You can build and version this image using make targets.
+
+```sh
+make build       # Builds the image locally
+make version     # Builds the image and creates version tags
+make list-images # Shows all tagged versions of the image
+make clean       # Deletes all tagged versions of the image
+```
+
+## How to Run
+
+You can use this image to deploy a site from your local machine.
+
+1. Build the `wpengine/site-deploy:latest` image with `make build`.
+2. Change directories into the root of the local site you'd like to deploy.
+3. Create a `.env` file with the following variables, changing their values as needed.
+
+```sh
+INPUT_WPE_ENV=yourinstall # The target WP Engine install name.
+GITHUB_REF=main           # Inconsequential, but must be defined for now.
+INPUT_REMOTE_PATH=
+INPUT_SRC_PATH=.
+INPUT_PHP_LINT=TRUE
+INPUT_CACHE_CLEAR=TRUE
+```
+
+3. Set an environment variable with your private SSH key, replacing the key file name with your own.
+
+```sh
+export INPUT_WPE_SSHG_KEY_PRIVATE=`cat ~/.ssh/my_sshg_key_rsa`
+```
+4. Replace `/path/to/your/install` with the absolute path to your local site and run the deploy!
+
+```sh
+ docker run \
+    -e "INPUT_WPE_SSHG_KEY_PRIVATE" \
+    -e "INPUT_FLAGS=-azvr --inplace --exclude=\".*\"" \
+    --env-file ./.env \
+    -v /path/to/your/install:/site \
+    --workdir=/site \
+    wpengine/site-deploy:latest
+```