Update submission button

attempt to align centre, change colour to white for better visibility, insert distance to text

index.html

@@ -180,7 +180,7 @@ <h3 class="center-text color-white no-margin-top thumbnail-title">Submission</h3
                             <div class="caption">
                                 <!-- Link of the submission-->
                                 <p class="color-black justify margin-bottom-button-half p-section">Submit your abstract through the following link:</p>
-                                <p class="color-black justify p-section"><a href="https://data-ethics.sciencescall.org/" target="_blank" class="button-link button-round">
+                                <p class="color-black justify p-section" style="text-align: center; margin-top: 10px;"><a href="https://data-ethics.sciencescall.org/" target="_blank" class="button-link button-round">
                                     https://data-ethics.sciencescall.org/
                                 </a>
                             </p>