feat: adds hover hint to matrix view

projects/mastolists/src/app/followings/matrix/matrix.component.html

@@ -10,7 +10,9 @@
         <table>
             <thead>
             <tr>
-                <th></th>
+                <th style="vertical-align: bottom;">
+                   Hover over a contact or click on it to see more info about the following
+                </th>
                 <th *ngFor="let list of lists$ | async" class="list-title">
                     {{list.title}}
                 </th>