Make it more clear what date/time formats are supported out of the box

[sequba]

Description

• reorganize the information in the date-and-time-handling guide to distinguish better the date/time formats that are supported out of the box and the formats that need custom implementations of parse* and stringify* functions.

Links

https://hyperformula.handsontable.com/guide/date-and-time-handling.html https://handsoncode.slack.com/archives/C031GBX62SE/p1672832825163179 (internal discussion)

Type of issue

• [ ] Missing documentation
• [ ] Error in the documentation
• [ ] Request for a demo
• [ ] Request for a tutorial, guide etc.
• [x] Other issues, suggestions or ideas