Update README.md

Author: oli414

README.md

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 RCT Graphics Helper is an add-on for Blender 2.79 that aids the creation of sprites that match the graphical style of Rollercoaster Tycoon.
 
-![image](https://user-images.githubusercontent.com/2348094/163599017-243ab3a5-5567-4cd2-91d5-565b0cc86e63.png)
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+  <img src="https://user-images.githubusercontent.com/2348094/163599017-243ab3a5-5567-4cd2-91d5-565b0cc86e63.png">
+</p>
 
 # Prerequisites