Update readme

Author: vincefn

README.rst

@@ -28,7 +28,7 @@ This package can be installed from source using ``python setup.py install`` or `
 Examples
 --------
 
-The simplest way to use pyvkfft is to use the pyvkfft.fft interface, which will
+The simplest way to use pyvkfft is to use the ``pyvkfft.fft`` interface, which will
 automatically create the VkFFTApp (the FFT plans) according to the type of GPU
 arrays (pycuda, pyopencl or cupy), and also cache these apps:
 
@@ -43,6 +43,12 @@ arrays (pycuda, pyopencl or cupy), and also cache these apps:
   # This will compute the fft to a new GPU array
   d1 = fftn(d0)
 
+  # An in-place transform can also be done by specifying the destination
+  d0 = fftn(d0, d0)
+
+  # Or an out-of-place transform to an existing array (the destination array is always returned)
+  d1 = fftn(d0, d1)
+
 See the scripts and notebooks in the examples directory.
 An example notebook is also `available on google colab
 <https://colab.research.google.com/drive/1YJKtIwM3ZwyXnMZfgFVcpbX7H-h02Iej?usp=sharing>`_.