chore: added inl to cpp config (#12710)

Screenshot:
<img width="1027" alt="image"
src="https://github.com/zed-industries/zed/assets/19250981/1d35d35c-d31c-4feb-b2ca-a417972fadf6">

Release Notes:

- Added `inl` to cpp config ([12605](https://github.com/zed-industries/zed/issues/12605))

assets/icons/file_icons/file_types.json

@@ -74,6 +74,7 @@
     "ib": "storage",
     "ico": "image",
     "ini": "settings",
+    "inl": "cpp",
     "j2k": "image",
     "java": "java",
     "jfif": "image",