fix(notifications): keywords button is full width

The button to add keywords takes up the full width available. Should be much slimmer.

Author: hazzuk

res/css/views/elements/_TagComposer.pcss

@@ -12,6 +12,7 @@ Please see LICENSE files in the repository root for full details.
         flex-direction: row;
 
         .mx_AccessibleButton {
+            width: fit-content; /* prevent full width */
             min-width: 70px;
             padding: 0 8px; /* override from button styles */
             align-self: stretch; /* override default settingstab style */