Use ES6 template strings

src/qml/Chat/RoomHeader.qml

@@ -68,13 +68,13 @@ Rectangle {
         }
 
         HToolTip {
-            text: name && topic ? (name + "<br>" + topic) : (name || topic)
+            text: name && topic ? (`${name}<br>${topic}`) : (name || topic)
             label.textFormat: Text.StyledText
             visible: text && (nameHover.hovered || topicHover.hovered)
 
             readonly property string name:
                 roomName.truncated ?
-                ("<b>" + chatPage.roomInfo.display_name + "</b>") : ""
+                (`<b>${chatPage.roomInfo.display_name}</b>`) : ""
             readonly property string topic:
                 roomTopic.truncated ?  chatPage.roomInfo.topic : ""
         }

src/qml/Chat/Timeline/EventContent.qml

@@ -19,7 +19,7 @@ HRowLayout {
     readonly property string timeText: Utils.formatTime(model.date, false)
     readonly property string localEchoText:
         model.is_local_echo ?
-        "&nbsp;<font size=" + theme.fontSize.small + "px>⏳</font>" :
+        `&nbsp;<font size=${theme.fontSize.small}px>⏳</font>` :
         ""
 
     readonly property bool pureMedia: ! contentText && linksRepeater.count
@@ -97,15 +97,14 @@ HRowLayout {
                 // For some reason, if there's only one space,
                 // times will be on their own lines most of the time.
                 "  " +
-                "<font size=" + theme.fontSize.small +
-                "px color=" + theme.chat.message.date + '>' +
+                `<font size=${theme.fontSize.small}px ` +
+                      `color=${theme.chat.message.date}>` +
                 timeText +
                 "</font>" +
 
                 // Local echo icon
                 (model.is_local_echo ?
-                 "&nbsp;<font size=" + theme.fontSize.small +
-                 "px>⏳</font>" : "")
+                 `&nbsp;<font size=${theme.fontSize.small}px>⏳</font>` : "")
 
             transform: Translate { x: xOffset }