#7513113 BlazePress: Set up translation function

Setting up translation function for the DSP Widget.

Testing

1. Apply this diff.
2. Make sure you have a widget version that includes the patch mentioned in this P2: pMyNb-5Gd-p2
3. Open the widget in Calypso with an account in a different language than English.
4. Verify you see the main title translated (this works because the Promote your posts string is already translated in Calypso):