Is foreplay before relations encouraged in Islam?

Yes, affection and playfulness before intimacy are encouraged so that both spouses are ready and experience happiness.
The Prophet ﷺ asked Jabir RA why he had not married a young maiden so that they could play and be affectionate with one another. Intimacy is worship when done with a good intention, and the Qur'an reminds husbands to 'send forth' good for themselves. The husband must also ensure his wife reaches satisfaction too, as that is part of intimate maintenance and care. See Marital etiquette.