Adds Common Second Language quirk, tweaks to partial understanding (#90614)

## About The Pull Request

- Tweaks partial understanding. 

Paragraphs are now split into sentences first creating more natural
breaks between sentences.

- Adds "Common Second Language" quirk

This quirk changes your default understanding of common (up to) 90%
(your choice), meaning you drop the occasional word.


![image](https://github.com/user-attachments/assets/63e9d67b-7db2-4d23-9d0f-bae175962db4)


![image](https://github.com/user-attachments/assets/840ef391-5126-4ba7-9298-804686bcd6df)

Additionally, when your sanity drops below a threshold, you become
forced to speak your native language, albeit with a partial
understanding applied for everyone else.

Incompatible with similar language quirks + can't be taken by humans
(yet?)

## Why It's Good For The Game

Just a fun way to play around with the new "partial understanding"
system.

## Changelog

🆑 Melbert
add: "Common Second Language" quirk
qol: Language translations chunk sentences together better, making
partial understanding a bit easier to parse.
/🆑

code/modules/client/preferences/language.dm

@@ -83,3 +83,21 @@
 
 /datum/preference/choiced/language_skill/apply_to_human(mob/living/carbon/human/target, value)
 	return
+
+/datum/preference/choiced/csl_strength
+	category = PREFERENCE_CATEGORY_MANUALLY_RENDERED
+	savefile_key = "csl_strength"
+	savefile_identifier = PREFERENCE_CHARACTER
+	can_randomize = FALSE
+
+/datum/preference/choiced/csl_strength/create_default_value()
+	return "90%"
+
+/datum/preference/choiced/csl_strength/is_accessible(datum/preferences/preferences)
+	return ..() && (/datum/quirk/csl::name in preferences.all_quirks)
+
+/datum/preference/choiced/csl_strength/init_possible_values()
+	return list("90%", "75%", "50%", "33%", "25%", "10%")
+
+/datum/preference/choiced/csl_strength/apply_to_human(mob/living/carbon/human/target, value)
+	return