Update README.md

Adds image and updated credit

Author: paulmsmith

README.md

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 # GOVUK Design System Flow Diagrams for Miro
 A [Miro](https://miro.com) version of a popular [GOVUK Design System](https://gov.uk/design-system) based flow diagram developed by the GOVDESIGN community.
 
+![GitHub Logo](preview.png)
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 Use this file in Miro to create flow diagrams of GOV.UK services or Unbranded services that are based on the GOVUK Design System.
 
-Credit to Dave House who's Sketch version inspired this Miro version.
+Credit to Dave House who's [Sketch version](https://github.com/dashouse/govuk-design-system-flow-diagrams) inspired this Miro version.