add `lz4` module doc

docs/modules/gc.md

@@ -3,7 +3,6 @@ icon: package
 label: gc
 ---
 
-
 ### `gc.collect()`
 
 Invoke the garbage collector.

docs/modules/lz4.md

@@ -0,0 +1,14 @@
+---
+icon: package
+label: lz4
+---
+
+!!!
+This module is optional. Set option `PK_BUILD_MODULE_LZ4` to `ON` in your `CMakeLists.txt` to enable it.
+!!!
+
+LZ4 compression and decompression.
+
+#### Source code
+
+:::code source="../../include/typings/lz4.pyi" :::

include/typings/lz4.pyi

@@ -5,7 +5,7 @@ def compress(data: bytes) -> bytes:
     """
 
 def decompress(data: bytes) -> bytes:
-    """Decompress the given LZ4 block format data produced by lz4.compress().
+    """Decompress the given LZ4 block format data produced by `lz4.compress()`.
     
     This function is equivalent to `lz4.block.decompress` of https://pypi.org/project/lz4/.
     """