enh(NcRichContenteditable): Add optional visual label for content editable

[susnux]

☑️ Resolves

For consistent look of Nextcloud components this adds the same label as NcTextField / NcInputField / NcTextArea.

🖼️ Screenshots

vokoscreenNG-2023-12-03_19-26-38.mp4

🏁 Checklist

• ⛑️ Tests are included or are not applicable
• 📘 Component documentation has been extended, updated or is not applicable

[susnux]

A use case could be: nextcloud/server#41884

[ShGKme]

Works fine. Was broken to me by JetBrains Grazie browser extension...

[Antreesy]

Note (more for myself, but maybe we should mark it in the changleog): additional <div> wrapper around the input breaks styles, currently applied directly with <NcRichContenteditable class="custom-styling" />

[ShGKme]

Note (more for myself, but maybe we should mark it in the changleog): additional <div> wrapper around the input breaks styles, currently applied directly with <NcRichContenteditable class="custom-styling" />

That is expected (was discussed in the original issue). But formally, it is not a breaking change, because it doesn't change component's public interface and styles in Talk changed internal styles, not positioning styles.