Add 2023 Data

[slowe]

The CSV files should be added/updated in 2023-DFES/data/scenarios/primaries/. Do not use spaces in the file names as this has potential to break things.

You may need to update the file name references in 2023-DFES/data/scenarios/index.json if you have changed the file names. If you are adding different parameters to last year, you will also need to update 2023-DFES/data/scenarios/config.json as appropriate.

[NPgMattL]

Positive confirmation that I've picked this issue up.