Embedded dev mode

As a user I would like to make use of this while developing my own applications that will use the logpanel in production so that I can have a seamless experience between development and diagnosing/fixing issues in prod.

## Possible Solution
Since the logpanel pulls its logs from a centralised graylog, we cannot hook everyone's development environment into graylog. Not only would it cause chaos due to the volume of logs, it may present conflict/privacy issues.

A solution is to make some kind of "embedded" logpanel, perhaps a large container that holds the logpanel and graylog together. So a user can run something like

```shell
docker run -d --rm --port 9200:9200 --port 9300:9300 --port 8080:8080 gchr.io/diamondlightsource/logpanel-dev
```

This would expose a graylog instance at http://localhost:9200 and 9300, and a logpanel instance on http://localhost:8080, the user would then have to configure their application to point to the local graylog.

`logpanel-dev` _could_ also serve as a devcontainer for developing the logpanel itself, so this may also be a solution to #15

## Acceptance Criteria
- A user can easily (ideally with one command) run a local version of the logpanel
- They can point applications they are developing at it using simple graylog configuration