[GUIDE] How to create a translation for HyperFormula functions

Description

After we finish a few hundred formulas we would need to copy & paste (it's not a creative work*) translations for them.

• Where i18n are stored
• How do we format it, linter config
• PR rules
• CLA and copyright

• Guide should suggest that the translations are already known. Other spreadsheet apps agreed (mostly) and we should stick to the trend. We can link to sources. It would be best to use Open Office / Libre Office as they are open source and not copyrighted that much. Maybe we have a source that descriptions can be copied as well, we have to check the licensing first. (by @warpech: we do not have descriptions right now, see #2)

Links

i18n directory: https://github.com/handsontable/hyperformula/tree/master/src/i18n
We can direct to a source like: https://support.office.com/pl-pl/article/funkcje-programu-excel-lista-alfabetyczna-b3944572-255d-4efb-bb96-c6d90033e188

It is a transferred issue, original author: @wojciechczerniak

Start by reviewing the src/i18n directory and the checklist in the issue. Document where translations are stored, their format and linter configuration, PR rules, CLA and copyright requirements, and permitted reference sources; the guide is done when it covers each listed point and the licensing guidance is clear.