docs(managers/pip-compile): update list of source files and managers (#34030)

lib/modules/manager/pip-compile/readme.md

@@ -33,10 +33,12 @@ In turn `pip-compile` manager will find all source files and parse them as packa
 
 The following files are currently supported:
 
-| Source filename | Manager            |
-| --------------: | ------------------ |
-|      `setup.py` | `pip_setup`        |
-|          `*.in` | `pip_requirements` |
+|  Source filename | Manager            |
+| ---------------: | ------------------ |
+|       `setup.py` | `pip_setup`        |
+|      `setup.cfg` | `setup-cfg`        |
+| `pyproject.toml` | `pep621`           |
+| `*.in` / `*.txt` | `pip_requirements` |
 
 Example header:
 
@@ -60,6 +62,12 @@ Because `pip-compile` will update source files with their associated manager you
   },
   "pip_setup": {
     "enabled": false
+  },
+  "setup-cfg": {
+    "enabled": false
+  },
+  "pep621": {
+    "enabled": false
   }
 }
 ```