Support for Python 3.13

[Mr-Sunglasses]

• Add Support for Python 3.13 and update CI accordingly
• Drop Support for Python 3.8 ref. Python 3.8 is officially now unsupported #1042

[Mr-Sunglasses]

Hey @sansyrox I'm working on adding support for 3.13 but one of the , Related: #957 as it does not support latest pyo3

It's good that we can migrate to https://github.com/PyO3/pyo3-async-runtimes?tab=readme-ov-file or anything else that you can suggest.

[sansyrox]

Hey @Mr-Sunglasses 👋

Let's do this for the interim. Longer term, we will have to get rid of it altogether.

[sansyrox]

https://github.com/emmett-framework/granian/blob/master/src/runtime.rs

https://github.com/emmett-framework/granian/blob/master/src/callbacks.rs

We should implement something like the above if possible. Can you have a look at this @Mr-Sunglasses ?

[sansyrox]

#1086

Need to revert this