widget field validation is not respected

[stefanprobst]

when a custom richtext-field widget defines required fields in their schema, the validation is not respected and the document can be saved even when the required fields have not been filled out.

repro: https://github.com/stefanprobst/issue-keystatic-widget-field-validation

steps to reproduce:

• clone the above repo
• pnpm install && pnpm run dev
• open http://localhost:3000/keystatic
• create a new Post and add a "Widget" widget, without filling out anything, and click Save
• the document is saved even though the "Widget" has a required field in its schema: https://github.com/stefanprobst/issue-keystatic-widget-field-validation/blob/fb9c2048134d1e9dc2e4eb9e81073cd786d56cfe/keystatic.config.tsx#L26