docs: add Docker quickstart (#2875)

* Fix docker-compose file

* Add docker quickstart

docs/quickstart/generic.md

@@ -0,0 +1,49 @@
+## Prerequisites
+
+Please [install Coder](./install.md) before proceeding with the steps outlined in this article.
+
+## Creating your first template and workspace
+
+In a new terminal window, run the following to copy a sample template:
+
+```bash
+coder templates init
+```
+
+Follow the CLI instructions to select an example that you can modify for your
+specific usage (e.g., a template to **Develop code-server in Docker**):
+
+1. Navigate into your new templates folder and create your first template using
+   the provided command (e.g., `cd ./docker-code-server && coder templates create`)
+
+1. Answer the CLI prompts; when done, confirm that you want to create your template.
+
+Create a workspace using your template:
+
+```bash
+coder create --template="yourTemplate" <workspaceName>
+```
+
+Connect to your workspace via SSH:
+
+```bash
+coder ssh <workspaceName>
+```
+
+You can also access your workspace using the **access URL** you provided when
+deploying Coder (if you're using a temporary deployment and you opted to use
+Coder's tunnel, use the access URL you were provided). Log in with the admin
+credentials provided to you by Coder.
+
+![Coder Web UI with code-server](images/code-server.png)
+
+## Modifying templates
+
+You can edit the Terraform template as follows:
+
+```sh
+coder templates init
+cd gcp-linux # modify this line as needed to access the template
+vim main.tf
+coder templates update gcp-linux # updates the template
+```