Very small example added for st_geometrytype

[DrewScatterday]

When working with ST_GeometryType I was confused on what types the enum returned as well as proper usage of it

I won't be offended if you feel this is unnecessary as its a very small nit-picky change but just thought it would be helpful to add an example. Thanks for your hardwork!

[Maxxen]

Hi! Thanks a lot for this PR and the help on improving the docs.
This should probably also be documented, but the source-of-truth for the function reference is in the c++ files themselves, the markdown is automatically generated by executing the generate_function_reference.py script in the root of the directory.

To add an example for e.g. ST_GeometryType you'd have to add it to the DOC_EXAMPLE string in src/spatial/core/functions/scalar/st_geometrytype.cpp:90. Then recompile and execute the generate_funciton_reference.py script.

If this seems like a lot of effort feel free to leave this PR open as is and I will try to pick it up and incorporate the changes next time im working on spatial!

We're planning to rework this in the future so that all functions are declared separately with their names/parameters/types/overloads/descriptions/examples in e.g. json files from which we can generate both the markdown docs and scaffold the c++ stubs from.

[DrewScatterday]

No prob I'll look into this when I get a chance 👍

[DrewScatterday]

I reverted back the .md file that I manually changed and updated the function doc spec in the .cpp file but I need to troubleshoot my windows subsystem for linux setup so I can generate the build folder and then run generate_function_reference.py

[DrewScatterday]

Okay whew, so I was able to setup my linux env with cmake, gcc, openssl, and ninja. I then was able to successfully do make debug (which took quite a while the first time which I think is expected since I was building everything) and then run generate_function_reference.py

The one odd thing is there a few function doc changes that I didn't add so I'm wondering if my fork wasn't up to date when I built or something? Let me know if I'm missing something @Maxxen