Add signatures for diff

Author: kgryte

signatures/mathematical-functions-elementwise/diff.md

@@ -0,0 +1,41 @@
+# diff
+
+## NumPy
+
+```
+numpy.diff(a, n=1, axis=-1, prepend=<no value>, append=<no value>) → ndarray
+```
+
+## CuPy
+
+```
+cupy.diff(a, n=1, axis=-1, prepend=None, append=None) → ndarray
+```
+
+## dask.array
+
+```
+dask.array.diff(a, n=1, axis=- 1, prepend=None, append=None) → array
+```
+
+## JAX
+
+```
+jax.numpy.diff(a, n=1, axis=-1, prepend=None, append=None) → ndarray
+```
+
+`prepend` and `append` must be array-like.
+
+## PyTorch
+
+```
+torch.diff(input, n=1, dim=-1, prepend=None, append=None) → Tensor
+```
+
+## TensorFlow
+
+```
+tf.experimental.numpy.diff(a, n=1, axis=-1) → Tensor
+```
+
+No support for `prepend` and `append` (as of v2.16.1).