[Feature] Allow Particle Spawner particles to have customizable drag

[CatsAndChaos]

Particles created by a Particle Spawner have drag, which hinders their use in some cases. This prevents slow particles from traveling any meaningful distance. For particles going straight in one direction, e.g. in a chimney, the particles near their origin are moving quickly, while at the end of the plume there is a dense cloud of barely-moving particles.