API documentation missing links

[ptheywood]

In a number of places (atleast 6) there are links intending to link to API docs, which do not do so.

The ones i've found are of the pattern:

Full API documentation for the ``X``: link

Where X is the name of a class, such aas EnvironmentDescription.

We could hardcode links to the hosted API docs, but this feels brittle. There should be a breathe/exhale way of finding the correct link, although I'm not sure exactly how.

Additionally, as the api docs are an optional part of the docs project, these links will only exist if the API docs are being built, which is (suprisingly) expensive in terms or time.

• src/guide/6-agent-birth-death/1-agent-birth-device.rst:149
• src/guide/6-agent-birth-death/3-agent-death.rst:53
• src/guide/2-model-definition/3-agent.rst:152
• src/guide/2-model-definition/2-environment.rst:137
• src/guide/2-model-definition/1-model.rst:31
• src/guide/3-behaviour-definition/1-defining-agent-functions.rst:170

[Robadob]

Noticed some other issues on this page: https://docs.flamegpu.com/guide/3-behaviour-definition/6-host-functions.html

Bullets not formatted correctly:

Something odd going on around uniform here:

[Robadob]

I wasn't aware of this issue when I was fixing cross ref's the other day, only noticed this earlier today, will try and address all the issues tomorrow. Just noticed they're cross ref's to API docs, might be a tad harder....

[Robadob]

https://exhale.readthedocs.io/en/latest/usage.html#linking-to-a-generated-file

This appears to be the guidance, will test.

[Robadob]

Ok so writing

* Full API documentation for the ``EnvironmentDescription``: :class:`flamegpu::EnvironmentDescription`

produces a link like this.

And the link goes to api/classflamegpu_1_1_environment_description.html#_CPPv4N8flamegpu22EnvironmentDescriptionE

[Robadob]

And if you want custom text, you use something like this

* Full API documentation for the ``EnvironmentDescription``: :class:`custom text<flamegpu::EnvironmentDescription>`

Not clear how to get rid of the inline code style, but that's probably not an issue, this will just allow us to omit the namespace inline.

[Robadob]

The more info block at the bottom of src/guide/6-agent-birth-death/3-agent-death.rst:53 isn't even relevant, it appears copy pasted from a page related to environment.