fix gfx.posteffects docs

doc/en/scripting/builtins/libgfx-posteffects.md

@@ -15,28 +15,28 @@ The effect slot is a resource and must be declared in resources.json in the root
 ```lua
 -- Returns the index of the effect slot by name (pack:slot_name).
 -- If the specified slot does not exist, returns -1
-gfx.posteffect.index(name: str) --> int
+gfx.posteffects.index(name: str) --> int
 
 -- Assigns the effect to the slot
-gfx.posteffect.set(slot: int, effect: str)
+gfx.posteffects.set_effect(slot: int, effect: str)
 
 -- Returns the effect intensity (from 0.0 to 1.0)
 -- If the slot is empty, returns 0.0
-gfx.posteffect.get_intensity(slot: int) --> number
+gfx.posteffects.get_intensity(slot: int) --> number
 
 -- Sets the effect intensity (from 0.0 to 1.0)
 -- (The correctness of processing the parameter between 0.0 and 1.0 
 -- depends on the effect)
-gfx.posteffect.set_intensity(slot: int, intensity: number)
+gfx.posteffects.set_intensity(slot: int, intensity: number)
 
 -- Returns true if the slot is not empty and the effect intensity is non-zero
-gfx.posteffect.is_active(slot: int) --> bool
+gfx.posteffects.is_active(slot: int) --> bool
 
 -- Sets parameters values ('param' directives)
-gfx.posteffect.set_params(params: table)
+gfx.posteffects.set_params(slot: int, params: table)
 
 -- Sets values to an array
-gfx.posteffect.set_array(
+gfx.posteffects.set_array(
     -- effect slot index
     slot: int,
     -- parameter (array) name