DOC: add explanation of dtype to parameter values for np.append

Author: tuhinsharma121

numpy/lib/_function_base_impl.py

@@ -5715,7 +5715,10 @@ def append(arr, values, axis=None):
         These values are appended to a copy of `arr`.  It must be of the
         correct shape (the same shape as `arr`, excluding `axis`).  If
         `axis` is not specified, `values` can be any shape and will be
-        flattened before use.
+        flattened before use. If dtype of values is different from the
+        dtype of arr then their dtypes are compared to figure out the
+        common dtype they can both be safely coerced to. For e.g. `int64`
+        and `float64` can both go to `float64`.
     axis : int, optional
         The axis along which `values` are appended.  If `axis` is not
         given, both `arr` and `values` are flattened before use.