text-splitters[minor]: Add lua code splitting (#20421)

- **Description:** Complete the support for Lua code in
langchain.text_splitter module.
- **Dependencies:** No
- **Twitter handle:** @saberuster

If no one reviews your PR within a few days, please @-mention one of
baskaryan, efriis, eyurtsev, hwchase17.

---------

Co-authored-by: Bagatur <baskaryan@gmail.com>

libs/text-splitters/langchain_text_splitters/character.py

@@ -571,6 +571,23 @@ class RecursiveCharacterTextSplitter(TextSplitter):
                 " ",
                 "",
             ]
+        elif language == Language.LUA:
+            return [
+                # Split along variable and table definitions
+                "\nlocal ",
+                # Split along function definitions
+                "\nfunction ",
+                # Split along control flow statements
+                "\nif ",
+                "\nfor ",
+                "\nwhile ",
+                "\nrepeat ",
+                # Split by the normal type of lines
+                "\n\n",
+                "\n",
+                " ",
+                "",
+            ]
         elif language == Language.HASKELL:
             return [
                 # Split along function definitions