v_mp5: implemented ironsights (see commit comment) Ironsights can be either code-driven or mostly animation-driven: • "ironsights" enum, default 0. If set to 1, will trigger the different layers and behaviours required, but will not offset the weapon. Consider it to be a "do the offset yourself" mode. 2 and above will match the different attachments available on the weapon. • "ironsight_fire_scale" float, ranges from 0 to 1, default 0.5. Choose how much scaling down to apply to the firing recoil animations while in any ironsights mode.