Use monospace font for room, message IDs in View Source modal (#9956)

Author: paragpoddar

res/css/structures/_ViewSource.pcss

@@ -27,6 +27,7 @@ limitations under the License.
         border-bottom: 1px solid $quinary-content;
         padding-bottom: $spacing-12;
         margin-bottom: $spacing-12;
+        font-family: monospace;
 
         .mx_CopyableText {
             word-break: break-all;