[FEATURE] Custom plugin fields are not translatable if theye are defined in flexform

[MarineAs]

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TYPO3 Setup

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[calien666]

At the moment, FlexForm is not supported while translating. Only filed type input (standard) and textarea are supported due to restrictions in Core translation handling.
This was discussed several times until now, see #71 (comment).

As this is not a bug, but we could implement as feature, take a look at this comment: #285 (comment)

Currently adding flexform support, will take a lot of code changes and changes in current work steps. This is a big change, we can't effrt at the moment. If you think, you will sponsor this feature, please contact @borishinzer.

[calien666]

Duplicates #285