updated release notes

Author: KrisThielemans

documentation/release_6.3.htm

@@ -79,7 +79,11 @@ <h3>Bug fixes</h3>
     </ul>
 
 <h3>Build system</h3>
-
+<ul>
+  <li>Enable more diagnostics in CMake when finding CERN's ROOT (we used to silence them)<br>
+    <a href=https://github.com/UCL/STIR/pull/1552>PR #1552</a>
+  </li>
+</ul>
 
 <h3>Known problems</h3>
     <p>See <a href=https://github.com/UCL/STIR/labels/bug>our issue tracker</a>.</p>
@@ -97,7 +101,11 @@ <h3>Changed functionality</h3>
 
 
 <h3>Bug fixes</h3>
-
+<ul>
+  <li>Fixed minor incompatibility with gcc-14 and clang-18 buy adding an extra include file<br>
+    <a href=https://github.com/UCL/STIR/pull/1552>PR #1552</a>
+  </li>
+</ul>
 
 <h3>Other code changes</h3>