Gives Screenshake an actual smoothing value versus just jumping over …

…a single frame (#6524)

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# About the pull request

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![image](https://github.com/cmss13-devs/cmss13/assets/158611449/58503bfd-0c2e-42b9-8534-8d2d01281d28)

![image](https://github.com/cmss13-devs/cmss13/assets/158611449/226062a7-0e76-40c0-b488-1a0481125ca6)

Basically in game rn, screenshake uses jump easing, which over the span
of a single frame sends you from your current screen position to the
location of the screenshake. This PR gives it cubic easing, which while
being one of the more 'rough' easing options, makes it look like your
FPS arent dropping.


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Screenshake looked extremely low FPS/jumpy and honestly over long
periods of screenshake like queen screech kinda made your eyes hurt.
CM's screenshake was one of the worst of any SS13 servers and had us
looking extremely dated.

Screenshake should be Screenshake,not give players motion sickness 

This PR fixes that, now with screenshake being heavily dependent on your
personal FPS choice, with those who choose to play on the server
FPS/lower FPS having whats more similarly to the older 'jumpy'
screenshake, while those on higher FPS have to deal with random low FPS
screenshake

The vids speak for themselves

# Testing Photographs and Procedure
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<details>
<summary>Screenshots & Videos</summary>

I have vids of what it looks like too for gun recoil but photoshop
refuses to render my videos so theyll come later

What it used to look like:
https://streamable.com/c4wk97

One of the worst examples of old screenshake (at 48fps)
https://streamable.com/iyj8d7

What it looks like now (note I use 48 FPS for first one, then server FPS
for low fps ones)
https://streamable.com/5nd11l

</details>

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# Changelog

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:cl:

qol: Makes screenshake look less low FPS/jumpy
/:cl:

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code/modules/mob/mob_helpers.dm

@@ -315,7 +315,7 @@ GLOBAL_LIST_INIT(limb_types_by_name, list(
 		message = replace_X.Replace(message, "CKTH")
 	return message
 
-#define PIXELS_PER_STRENGTH_VAL 24
+#define PIXELS_PER_STRENGTH_VAL 28
 
 /proc/shake_camera(mob/M, steps = 1, strength = 1, time_per_step = 1)
 	if(!M?.client || (M.shakecamera > world.time))
@@ -326,10 +326,10 @@ GLOBAL_LIST_INIT(limb_types_by_name, list(
 	var/old_X = M.client.pixel_x
 	var/old_y = M.client.pixel_y
 
-	animate(M.client, pixel_x = old_X + rand(-(strength), strength), pixel_y = old_y + rand(-(strength), strength), easing = JUMP_EASING, time = time_per_step, flags = ANIMATION_PARALLEL)
+	animate(M.client, pixel_x = old_X + rand(-(strength), strength), pixel_y = old_y + rand(-(strength), strength), easing = CUBIC_EASING | EASE_IN, time = time_per_step, flags = ANIMATION_PARALLEL)
 	var/i = 1
 	while(i < steps)
-		animate(pixel_x = old_X + rand(-(strength), strength), pixel_y = old_y + rand(-(strength), strength), easing = JUMP_EASING, time = time_per_step)
+		animate(pixel_x = old_X + rand(-(strength), strength), pixel_y = old_y + rand(-(strength), strength), easing = CUBIC_EASING | EASE_IN, time = time_per_step)
 		i++
 	animate(pixel_x = old_X, pixel_y = old_y,time = clamp(floor(strength/PIXELS_PER_STRENGTH_VAL),2,4))//ease it back