Docs site (#269)

* Set up documentation site using jekyll

* Add workflow for deploying docs

* Ini formatting is hard to read

* Add instructions on how to run docs locally

* Work through docs

* Remove content from README

* Miscellaneous fixes

* Fix artifact upload

docs/how-tos/handle-file-uploads-using-third-party-tools.md

@@ -0,0 +1,44 @@
+---
+title: Handle file uploads using third party tools
+layout: default
+parent: How Tos
+nav_order: 10
+---
+
+# Handle file uploads using third party tools
+
+If you want to use an unsupported storage backend, or want to use a third party (e.g. rsync, rclone) tool for file uploads, you can build a Docker image containing the required binaries off this one, and call through to these in lifecycle hooks.
+
+For example, if you wanted to use `rsync`, define your Docker image like this:
+
+```Dockerfile
+FROM offen/docker-volume-backup:v2
+
+RUN apk add rsync
+```
+
+Using this image, you can now omit configuring any of the supported storage backends, and instead define your own mechanism in a `docker-volume-backup.copy-post` label:
+
+```yml
+version: '3'
+
+services:
+  backup:
+    image: your-custom-image
+    restart: always
+    environment:
+      BACKUP_FILENAME: "daily-backup-%Y-%m-%dT%H-%M-%S.tar.gz"
+      BACKUP_CRON_EXPRESSION: "0 2 * * *"
+    labels:
+      - docker-volume-backup.copy-post=/bin/sh -c 'rsync $$COMMAND_RUNTIME_ARCHIVE_FILEPATH /destination'
+    volumes:
+      - app_data:/backup/app_data:ro
+      - /var/run/docker.sock:/var/run/docker.sock
+
+  # other services defined here ...
+volumes:
+  app_data:
+```
+
+{: .note }
+Commands will be invoked with the filepath of the tar archive passed as `COMMAND_RUNTIME_BACKUP_FILEPATH`.