Update readme.md

readme.md

@@ -7,7 +7,7 @@ methods.
 
 The simulation can be paused by pressing the space bar. By clicking on a body,
 a windows will appear which allow to add a name, change its mass and/or its density. 
-THe simulation is automatically centered on the largest body.
+The simulation is automatically centered on the largest body.
 
 Launch via python3 main.py