Merge pull request #4685 from vespa-engine/johsol/first-phase-max

Add firstPhaseMax

Author: johansolbakken

en/reference/ranking/rank-features.html

@@ -1286,6 +1286,15 @@ <h3 id="rank-scores">Rank scores</h3></td></tr>
     </p>
   </td></tr>
 
+<tr><td>firstPhaseMax</td>
+  <td>-infinity</td>
+  <td>
+    <p id="firstPhaseMax">
+      The maximum first-phase rank score among all hits matched on the content node.
+      Calculated locally on each content node, so may yield different results on different nodes.
+    </p>
+  </td></tr>
+
 <tr><td>relevanceScore</td>
     <td>-</td>
     <td>