Merge pull request #136 from su2code/4th_conference_banner

Update frontpage with the 4th conference banner information.

Author: TobiKattmann

index.html

@@ -38,8 +38,9 @@ <h2 style="font-weight:700">Powerful. Fast. Free.</h2>
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-      <h1>3rd Annual SU2 Conference</h1>
-       <h3>Presentation slides and recordings will be available on the <a href="https://su2foundation.org/su2conference2022/">conference website</a>.</h3>
+      <h1>4th Annual SU2 Conference</h1>
+       <h3>The 4th edition of the SU2 conference takes place in Varenna/Italy on the 23rd - 25th of October.</h3>
+       <h3>Registration and abstract submission are open now and the links to the respective platforms together with all up-to-date information can be found on the <a href="https://su2foundation.org/su2conference2023/">conference website</a>.</h3>
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