Update ParticleEffect.h (scp-fs2open#7446)

Curve input follow-up to scp-fs2open#6926 and scp-fs2open#6889, in that it adds two new curve input Nebula and Particle Detail Levels for use within the particle effects table. These new inputs will allow modders to develop effects that can properly be optimized per varying particle and nebula detail levels.

Author: wookieejedi

code/particle/ParticleEffect.h

@@ -273,10 +273,12 @@ class ParticleEffect {
 			modular_curves_submember_input<&ParticleSource::getEffect, &SCP_vector<ParticleEffect>::size>,
 			ModularCurvesMathOperators::division>{}},
 		std::pair {"Total Particle Count", modular_curves_global_submember_input<get_particle_count>{}},
+		std::pair {"Particle Detail Level", modular_curves_global_submember_input<Detail, &detail_levels::num_particles>{}},
 		std::pair {"Particle Usage Score", modular_curves_math_input<
 		    modular_curves_global_submember_input<get_particle_count>,
 			modular_curves_global_submember_input<Detail, &detail_levels::num_particles>,
 			ModularCurvesMathOperators::division>{}},
+		std::pair {"Nebula Detail Level", modular_curves_global_submember_input<Detail, &detail_levels::nebula_detail>{}},
 		std::pair {"Nebula Usage Score", modular_curves_math_input<
 		    modular_curves_global_submember_input<get_particle_count>,
 			modular_curves_global_submember_input<Detail, &detail_levels::nebula_detail>,