Add Devcontainer configs

[nelson-lojo]

Added configuration to launch a devcontainer with Prairielearn launched simultaneously. The primary benefit of this is to enable demos/development without installing docker (or even an IDE!) locally -- see "Run in the cloud" below.

Run in the cloud / browser:

1. Click the "Code" dropdown on the page of this branch (will also work on master once merged)
2. Click the "Codespaces" tab
3. Click the "+" to create a new codespace
4. You will be dropped into a VSCode web editor
   • If you prefer your local IDE, then you can connect to the codespace via an extension (vscode | intellij)

Run locally:
0. Have docker installed (desktop | headless) and (if you installed docker engine) your user given docker execution/configuration permissions

1. Open this repo in your IDE
2. Launch the devcontainer as supported by your IDE

   • VSCode:

     1. Install the Devcontainers extension
     2. Open the Command Pallet (Ctrl+Shift+P (Windows,Linux) or Cmd+Shift+P (Mac)) and select "Dev Containers: Reopen in Container"

   • IntelliJ: see their docs

   • Other IDEs will likely require the devcontainers cli and a remote (similar to ssh) connection to the started container. This process is rather involved and somewhat unstable as of 12 June 2024. If your IDE supports it, I recommend connecting to a codespace as detailed above ("Run in the cloud").