Place holder support At other Areas

## Is your enhancement request related to a problem? Please describe

field Place holder is a good place for educating your user in how to use product. Currently are placeholder for question tile. Request to add other placeholders in following order of priority

1. Question body (I can educate user how to write good question)
2. Answer Body (I can educate user how to write good answer)
3. comment body (least priority - I can ask user to be polite, be respectfull etc)

## Describe the solution you'd like

A clear and concise description of what you want to happen.

## Describe alternatives you've considered

A clear and concise description of any alternative solutions or features you've considered.

Inizia individuando il placeholder esistente per il riquadro della domanda e segui come viene configurato e visualizzato il relativo testo. Estendi lo stesso flusso al corpo della domanda, al corpo della risposta e al corpo del commento, nell’ordine di priorità richiesto, quindi verifica che ogni editor visualizzi il placeholder configurato.

Scritto dal modello di indicizzazione a partire dal testo della issue.