Build a docker image for the production webapp

This uses the same http-server image as the development webapp, but
copies all non-plot files into the container. This ensures that the
container can be scanned for vulnerabilities.

The plots are stored in a mounted volume because they are generated by the
`viz_scripts` container and stored in the shared, mounted volume.

```
=> [internal] load build definition from Dockerfile                                                                                                                         0.0s
=> => transferring dockerfile: 42B                                                                                                                                          0.0s
=> [internal] load .dockerignore                                                                                                                                            0.0s
=> => transferring context: 2B                                                                                                                                              0.0s
=> [internal] load metadata for docker.io/danjellz/http-server:1.4                                                                                                          0.0s
=> [internal] load build context                                                                                                                                            0.0s
=> => transferring context: 1.76kB                                                                                                                                          0.0s
=> [1/4] FROM docker.io/danjellz/http-server:1.4                                                                                                                            0.0s
=> CACHED [2/4] RUN mkdir -p /public                                                                                                                                        0.0s
=> CACHED [3/4] COPY ../client /public/client                                                                                                                               0.0s
=> CACHED [4/4] COPY ../*.html /public                                                                                                                                      0.0s
=> exporting to image                                                                                                                                                       0.0s
=> => exporting layers                                                                                                                                                      0.0s
=> => writing image sha256:ff0154b07bbb0d6dc2e78343bf4f842fe2eee85c980ae04d4e01788356b6eab6                                                                                 0.0s
=> => naming to docker.io/em-pub-dash-prod/frontend                                                                                                                         0.0s
```

```
dashboard_1        | Starting up http-server, serving ./
dashboard_1        |
dashboard_1        | http-server version: 14.1.1
dashboard_1        |
dashboard_1        | http-server settings:
dashboard_1        | CORS: disabled
dashboard_1        | Cache: 3600 seconds
dashboard_1        | Connection Timeout: 120 seconds
dashboard_1        | Directory Listings: visible
dashboard_1        | AutoIndex: visible
dashboard_1        | Serve GZIP Files: false
dashboard_1        | Serve Brotli Files: false
dashboard_1        | Default File Extension: none
dashboard_1        |
dashboard_1        | Available on:
dashboard_1        |   http://127.0.0.1:8080
dashboard_1        |   http://172.20.0.4:8080
dashboard_1        | Hit CTRL-C to stop the server
dashboard_1        |
dashboard_1        | [2022-09-07T20:57:57.039Z]  "GET /" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Firefox/91.0"
dashboard_1        | (node:1) [DEP0066] DeprecationWarning: OutgoingMessage.prototype._headers is deprecated
dashboard_1        | (Use `node --trace-deprecation ...` to show where the warning was created)
dashboard_1        | [2022-09-07T20:57:57.127Z]  "GET /client/css/nrel.application.min.css" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Firefox/91.0"
dashboard_1        | [2022-09-07T20:57:57.128Z]  "GET /client/css/bootstrap.min.css" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Firefox/91.0"
dashboard_1        | [2022-09-07T20:57:57.129Z]  "GET /client/css/dashboard.css" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Firefox/91.0"
```

The resulting web page is displayed correctly

frontend/docker/Dockerfile

@@ -0,0 +1,5 @@
+FROM danjellz/http-server:1.4
+
+RUN mkdir -p /public
+COPY ../client /public/client
+COPY ../*.html /public