Added driver documentatnion

Author: JonasProgrammer

README.md

@@ -0,0 +1,57 @@
+---
+description: Hetzner Cloud driver for machine
+keywords: machine, hetzner, Hetzner Cloud, driver
+title: Hetzner Cloud
+---
+
+Create Docker machines on [Hetzner Cloud](https://docs.hetzner.cloud/).
+
+You need to create a project-sepcific access token under `Access` > `API Tokens` in the project control panel
+and pass that to `docker-machine create` with the `--hetzner-api-token` option.
+
+## Usage
+
+    $ docker-machine create --driver hetzner --hetzner-api-token=QJhoRT38JfAUO037PWJ5Zt9iAABIxdxdh4gPqNkUGKIrUMd6I3cPIsfKozI513sy some-machine
+    
+### Using environment variables
+
+    $ HETZNER_API_TOKEN=QJhoRT38JfAUO037PWJ5Zt9iAABIxdxdh4gPqNkUGKIrUMd6I3cPIsfKozI513sy HETZNER_IMAGE=centos-7 docker-machine create --driver hetzner some-machine
+    
+
+## Options
+
+-   `--hetzner-api-token`: **required**. Your project-specific access token for the Hetzner CLoud API.
+-   `--hetzner-image`: The name of the Hetzner Cloud image to use, see [Images API](https://docs.hetzner.cloud/#resources-images-get) for how to get a list.
+-   `--hetzner-server-type`: The type of the Hetzner Cloud server, see [Server Types API](https://docs.hetzner.cloud/#resources-server-types-get) for how to get a list.
+-   `--hetzner-server-location`: The location to create the server in, see [Locations API](https://docs.hetzner.cloud/#resources-locations-get) for how to get a list.
+-   `--hetzner-existing-key-path`: Use an existing (local) SSH key instead of generating a new keypair.
+-   `--hetzner-existing-key-id`: **requires `--hetzner-existing-key-path`**. Use an existing (remote) SSH key instead of uploading the imported key pair,
+    see [SSH Keys API](https://docs.hetzner.cloud/#resources-ssh-keys-get) for how to get a list
+
+The Hetzner Cloud driver will use `debian-9` as the default image and `g2-local` as the default type.
+
+#### Existing SSH keys
+
+When you specify the `--hetzner-existing-key-path` option, the driver will attempt to copy the `*(specified file name)*`
+and `*(specified file name).pub*` to the machine's store path. They public key file's permissions will be set according
+to your current `umask` and the private key file will have `600` permissions.
+
+When you additionally specify the `--hetzner-existing-key-id` option, the driver will not create an SSH key using the API
+but rather try to use the existing public key corresponding to the given id. Please note that during machine creation,
+the driver will attempt to [get the key](https://docs.hetzner.cloud/#resources-ssh-keys-get-1) and **compare it's
+fingerprint to the local public key's fingerprtint**. Keep in mind that the both the local and the remote key must be
+accessible and have matching fingerprints, otherwise the machine will fail it's pre-creation checks.
+
+Also note that the driver will attempt to delete the linked key during machine removal, unless `--hetzner-existing-key-id`
+was used during creation.
+
+#### Environment variables and default values
+
+| CLI option                          | Environment variable              | Default                    |
+| ----------------------------------- | --------------------------------- | -------------------------- |
+| **`--hetzner-api-token`**           | `HETZNER_API_TOKEN`               | -                          |
+| `--hetzner-image `                  | `HETZNER_IMAGE_IMAGE`             | `debian-9`                 |
+| `--hetzner-server-type`             | `HETZNER_TYPE`                    | `g2-local`                 |
+| `--hetzner-server-location`         | `HETZNER_LOCATION`                | - *(let Hetzner choose)*   |
+| `--hetzner-existing-key-path`       | `HETZNER_EXISTING_KEY_PATH`       | - *(generate new keypair)* |
+| `--hetzner-existing-key-id`         | `HETZNER_EXISTING_KEY_ID`         | 0 *(upload new key)*       |