Fix flavour screenshot styling in vanilla flavour

app/javascript/styles/mastodon/admin.scss

@@ -333,6 +333,22 @@ hr.spacer {
   }
 }
 
+.flavour-screen {
+  display: block;
+  margin: 10px auto;
+  max-width: 100%;
+}
+
+.flavour-description {
+  display: block;
+  font-size: 16px;
+  margin: 10px 0;
+
+  & > p {
+    margin: 10px 0;
+  }
+}
+
 .report-accounts {
   display: flex;
   flex-wrap: wrap;