Adding decimal support

[Caedin]

Adds a check for decimal types in the schema mapping. Attempts to map deltalake decimal types to pyarrow decimal types using a basic regex, and defaults to existing incorrect type message if no match is found.

[Caedin]

Testing

Setting up the table:

Insert some dummy data:

Sample of the output with the decimal type:

Trying to query the data using the delta reader 0.2.8 results in the following error:

After the fix, the query is successful, with the decimal types returning properly:

[jeppe742]

Will just merge it using my own branch, otherwise the tests will not work :)