feat: Add sample of new_with_encoders and infer_encoder

[tomasfarias]

Related issue: #31

Adds a sample to Python README showcasing new_with_encoders and infer_encoder. The sample is based on my current work on exporting Arrow data to PostgreSQL.

Tested the script locally with a PostgreSQL database running on localhost:5432, and the final table looks like:

postgres=# select * from id_properties;
 id |          properties          
----+------------------------------
  1 | {"age": 33, "name": "alice"}
  2 | {"age": 24, "name": "bob"}
  3 | {}
  4 | null
psothog=# \d id_properties
             Table "public.id_properties"
   Column   |  Type  | Collation | Nullable | Default 
------------+--------+-----------+----------+---------
 id         | bigint |           |          | 
 properties | jsonb  |           |          |

Besides this sample, I'd be happy to contribute more documentation. Are there any plans to host documentation pages somewhere? E.g. GitHub pages or readthedocs? I'd be happy to contribute the Sphinx boilerplate to get that going (at least for the Python API docs, not sure how to mix Rust and Python docs).

Thank you!

[adriangb]

Thanks so much for the contribution! I prefer mkdocs hosted on github pages, I can set it up at some point, but for now I'd say let's keep it in a README.md until that clearly is not enough.