Merge pull request #52 from Charlotte-Potter/add_alt_text

Doc update - added alt text. Update ApertureComponent.rst

Author: RebeccaHirst

source/builder/components/ApertureComponent.rst

@@ -11,6 +11,7 @@ Aperture Component
 
     .. image:: /images/aperture.gif
         :width: 60%
+		:alt: "A grey screen with a moving cirle, which is linked to a mouse. As the mouse is moved a photo of a landscape underneath is shown as if revealing a hidden image underneath."
 
 This component can be used to filter the visual display, as if the subject is looking at it through an opening (i.e. add an image component, as the background image, then add an aperture to show part of the image). Currently, in builder, only circular apertures are supported (you can change the shape by specifying your aperture in a code component- we are hoping to make it easier to do this through builder soon!). Moreover, only one aperture is enabled at a time. You can't "double up": a second aperture takes precedence. Currently this component **does not run online**  (`see the status of online options <https://www.psychopy.org/online/status.html>`_, but you can achieve something similar online using an image with a mask: see an `example demo here <https://run.pavlovia.org/demos/dynamic_selective_inspect/html/>`_ with corresponding `PsychoPy experiment files here <https://gitlab.pavlovia.org/demos/dynamic_selective_inspect>`_ or by using the `MouseView plugin <https://run.pavlovia.org/demos/mouseview_demo/>`_.
 
@@ -236,4 +237,4 @@ Validate with...
 
 	API reference for :class:`~psychopy.visual.Aperture`
 
-.. redirect-from:: aperture.rst
+.. redirect-from:: aperture.rst