Graph representation of configs in `ve_run.toml`

**Is your feature request related to a problem? Please describe.**
When we add python functions to visualise to tidy outputs, it'd be great to also include a simply function to draw the dependencies or flow between modules as configured in `ve_run.toml`. I think some users will use it to visually check that they have configured the dependencies correctly, before running the simulation.

The [documentation](https://virtual-ecosystem.readthedocs.io/en/latest/using_the_ve/example_data.html#configuration-files) of `config/ve_run.toml` was simple, but the example tutorial reveals `init = ` and `update = `. We should explain this in the tutorial page, and a graph would be helpful for the explanation.

**Describe the solution you'd like**
A simply python function to read `ve_run.toml` and generate a dependency flow chart.

Start by reading the ve_run.toml configuration documentation and the example tutorial, especially the use of init and update. Identify how configuration dependencies are represented, then define the graph output and add a Python function that generates the dependency flow chart. Done means the function reads ve_run.toml and the tutorial clearly explains the configuration and includes the graph.

Written by the indexing model from the issue text.