A new block has been added to get the game's language that users can set from Steam. This is different than the Stencyl block that gets the system language which might not be the same as the game's configured language. I've only tested English so far but based on Steam's documentation I would expect one of these results:
brazilian, bulgarian, czech, danish, dutch, english, finnish, french, german, greek, hungarian, italian, japanese, koreana, norwegian, polish, portuguese, romanian, russian, schinese, spanish, swedish, tchinese, thai, turkish, arabic, ukrainian
Update: I implemented Russian and Simplified Chinese into one of my games and can confirm that the text returned by the new block matches the options above.
Since this change required a rebuild and I didn't rebuild on Linux, this block will not function on Linux. It might also give an error so Linux users just stick to the previous version (V2).
May 18: small fix to return "english" when Steam isn't running to avoid errors.