adding a note for real input

Signed-off-by: Pradyot Ranjan <99216956+pradyotRanjan@users.noreply.github.com>

Author: prady0t

docs/api-reference.md

@@ -6,6 +6,7 @@
     :nosignatures:
     :toctree: generated
 
+    angle
     apply_where
     argpartition
     at
@@ -26,5 +27,4 @@
     setdiff1d
     sinc
     union1d
-    angle
 ```

src/array_api_extra/_lib/_funcs.py

@@ -840,6 +840,10 @@ def angle(z: Array, /, *, deg: bool = False, xp: ModuleType | None = None) -> Ar
         The counterclockwise angle from the positive real axis on the complex
         plane in the range ``(-pi, pi]``.
 
+    Notes
+    -----
+    A real input x is interpreted as x + 0j
+
     Examples
     --------
     >>> import array_api_strict as xp