[ADD] accounting/l10n_co: Add doc on automatic currency Colombia

[masi-odoo]

Add documentation on the automatic currency rate for CO which is an integration with the "Banco de la Republica" service.

Drive with photos: https://drive.google.com/drive/folders/1jdPv6PNF_ekTuNxqw9GXoIJgII9HN-Eh?usp=sharing

[robodoo]

[StraubCreative]

ci/minimal check is not passing because the branch name is not properly formatted (needs to start with Odoo version prefix e.g. 16.0, 17.0, 18.0, master so runbot can initiate).

Closing this PR and continuing over on #13967 ...