Update documentation regarding field mapping and KanjiVocab support

[shintoo]

Currently, the Readme makes no mention of KanjiVocab, but the provided card styles assume the plugin is installed and set up.

Also, please post your full field mapping when importing Formatting.txt. Not all of the fields are shown in the screenshot.

[Mauville]

Thank you for opening this issue :)

The part about KanjiVocab is here https://github.com/Mauville/Koohii2Anki?tab=readme-ov-file#finished-rtk
IIRC, the field should just be empty by default, so nothing should happen if the user doesn't have the plugin installed.

When loading formatted.txt, the defaults should work fine, although you are right in that the picture does not show them fully.
Have the fields changed? Or is there a specific reason for the full inclusion being needed?