Dev container documentation and cleanup

.devcontainer/README.md

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+# Development container
+
+Development container that can be used with VSCode.
+
+It works on Linux, Windows and OSX.
+
+## Requirements
+
+- [VS code](https://code.visualstudio.com/download) installed
+- [VS code remote containers extension](https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-containers) installed
+- [Docker](https://www.docker.com/products/docker-desktop) installed and running
+    - If you don't use Linux or WSL 2, share your home directory `~/` and the directory of your project with Docker Desktop
+- [Docker Compose](https://docs.docker.com/compose/install/) installed
+- Ensure your host has the following and that they are accessible by Docker:
+    - `~/.ssh` directory
+    - `~/.gitconfig` file (can be empty)
+
+## Setup
+
+1. Open the command palette in Visual Studio Code (CTRL+SHIFT+P).
+1. Select `Remote-Containers: Open Folder in Container...` and choose the project directory.
+
+## Customization
+
+### Customize the image
+
+You can make changes to the [Dockerfile](Dockerfile) and then rebuild the image. For example, your Dockerfile could be:
+
+```Dockerfile
+FROM qmcgaw/godevcontainer
+USER root
+RUN apk add curl
+USER vscode
+```
+
+Note that you may need to use `USER root` to build as root, and then change back to `USER vscode`.
+
+To rebuild the image, either:
+
+- With VSCode through the command palette, select `Remote-Containers: Rebuild and reopen in container`
+- With a terminal, go to this directory and `docker-compose build`
+
+### Customize VS code settings
+
+You can customize **settings** and **extensions** in the [devcontainer.json](devcontainer.json) definition file.
+
+### Entrypoint script
+
+You can bind mount a shell script to `/home/vscode/.welcome.sh` to replace the [current welcome script](shell/.welcome.sh).
+
+### Publish a port
+
+To access a port from your host to your development container, publish a port in [docker-compose.yml](docker-compose.yml).
+
+### Run other services
+
+1. Modify [docker-compose.yml](docker-compose.yml) to launch other services at the same time as this development container, such as a test database:
+
+    ```yml
+      database:
+        image: postgres
+        restart: always
+        environment:
+          POSTGRES_PASSWORD: password
+    ```
+
+1. In [devcontainer.json](devcontainer.json), change the line `"runServices": ["vscode"],` to `"runServices": ["vscode", "database"],`.
+1. In the VS code command palette, rebuild the container.