Add int16 to codegen (#4507)

esphome/codegen.py

@@ -63,6 +63,7 @@ from esphome.cpp_types import (  # noqa
     uint16,
     uint32,
     uint64,
+    int16,
     int32,
     int64,
     size_t,

esphome/cpp_types.py

@@ -14,6 +14,7 @@ uint8 = global_ns.namespace("uint8_t")
 uint16 = global_ns.namespace("uint16_t")
 uint32 = global_ns.namespace("uint32_t")
 uint64 = global_ns.namespace("uint64_t")
+int16 = global_ns.namespace("int16_t")
 int32 = global_ns.namespace("int32_t")
 int64 = global_ns.namespace("int64_t")
 size_t = global_ns.namespace("size_t")