Implement the Tabular Schema to declare tabular data

[dalonsoa]

Problem

Complementary to the CSV Dialect, this schema provides information about the contents of the columns in a standardised way, from column names to description of the content, its units or the type of the data, among many others. It will help to understand what the data in each column represent.

What is needed

Capture the Table Schema in a pydantic class, so it can be used where needed. Probably, it will be necessary at least 2 objects, one for the individual field descriptors and another one for the list of field descriptors and the other optional fields.

Using the schema in the load/save workflow is a separate issue.

[alexdewar]

Hacktoberfest task, maybe?

[dalonsoa]

I've updated the issue to use pydantic, which is much more usable and modern.