Improve accessibility based on HAN university accessibility report

Unfortunately, most issues are in Kirigami and we can't fix them from our side. Namely, these things remain unfixed: 
- `Kirigami.PlaceholderMessage` are not read by screen readers
- When navigating with the keyboard, pressing tab selects elements from right to left, which is weird
- When navigating with the keyboard, the selected element is not highlighted
- `Kirigami.Action` that don't have a `text` property don't use the `Accessible.name` property when using a screen reader.

app/qml/DevicePage.qml

@@ -20,7 +20,10 @@ Kirigami.ScrollablePage {
     actions: [
         Kirigami.Action {
             icon.name: "network-disconnect"
-            onTriggered: root.currentDevice.unpair()
+            onTriggered: {
+                root.currentDevice.unpair()
+                pageStack.pop(0)
+            }
             text: i18nd("kdeconnect-app", "Unpair")
             visible: root.currentDevice && root.currentDevice.isPaired
         },
@@ -122,6 +125,8 @@ Kirigami.ScrollablePage {
         ]
 
         Kirigami.PlaceholderMessage {
+            // FIXME: not accessible. screen readers won't read this. Idem for the other PlaceholderMessages
+            //        https://invent.kde.org/frameworks/kirigami/-/merge_requests/1482
             text: i18nd("kdeconnect-app", "This device is not paired")
             anchors.centerIn: parent
             visible: root.currentDevice && root.currentDevice.isReachable && !root.currentDevice.isPaired && !root.currentDevice.isPairRequestedByPeer && !root.currentDevice.isPairRequested
@@ -162,6 +167,8 @@ Kirigami.ScrollablePage {
         }
 
         Kirigami.PlaceholderMessage {
+            // FIXME: not accessible. screen readers won't read this.
+            //        https://invent.kde.org/frameworks/kirigami/-/merge_requests/1482
             visible: root.currentDevice && !root.currentDevice.isReachable
             text: i18nd("kdeconnect-app", "This device is not reachable")
             anchors.centerIn: parent

app/qml/Main.qml

@@ -104,7 +104,7 @@ Kirigami.ApplicationWindow {
                     enabled: status & DevicesModel.Reachable
                     checked: pageStack.currentItem && pageStack.currentItem.currentDevice == device
                     onClicked: {
-                        root.pageStack.clear()
+                        root.pageStack.pop(0)
                         root.pageStack.push(
                             Qt.resolvedUrl("DevicePage.qml"),
                             {currentDevice: device}

app/qml/PluginSettings.qml

@@ -30,6 +30,8 @@ Kirigami.ScrollablePage {
                     Layout.alignment: Qt.AlignVCenter
                     checked: model.isChecked
                     onToggled: model.isChecked = checked
+                    Accessible.name: model.name
+                    Accessible.description: model.description
                 }
 
                 ColumnLayout {
@@ -57,6 +59,9 @@ Kirigami.ScrollablePage {
                 Kirigami.Action {
                     icon.name: "settings-configure"
                     visible: configSource != ""
+                    // FIXME: not accessible. screen readers won't read this and just say "push button".
+                    //        https://bugreports.qt.io/browse/QTBUG-123123
+                    Accessible.name: i18nd("kdeconnect-app", "Configure plugin")
                     onTriggered: {
                         if (pageStack.lastItem.toString().startsWith("PluginInfoPage")) {
                             pageStack.lastItem.configFile = configSource;

app/qml/mpris.qml

@@ -62,6 +62,8 @@ Kirigami.Page
 
     Kirigami.PlaceholderMessage {
         id: noPlayersText
+        // FIXME: not accessible. screen readers won't read this.
+        //        https://invent.kde.org/frameworks/kirigami/-/merge_requests/1482
         text: i18nd("kdeconnect-app", "No players available")
         anchors.centerIn: parent
         visible: pluginInterface.playerList.length == 0

app/qml/runcommand.qml

@@ -46,6 +46,8 @@ Kirigami.ScrollablePage
         }
 
         Kirigami.PlaceholderMessage {
+            // FIXME: not accessible. screen readers won't read this.
+            //        https://invent.kde.org/frameworks/kirigami/-/merge_requests/1482
             visible: commandsList.count === 0
             text: i18nd("kdeconnect-app", "No commands defined")
             anchors.centerIn: parent

smsapp/qml/ConversationList.qml

@@ -243,6 +243,8 @@ Kirigami.ScrollablePage
         }
 
         Kirigami.PlaceholderMessage {
+            // FIXME: not accessible. screen readers won't read this.
+            //        https://invent.kde.org/frameworks/kirigami/-/merge_requests/1482
             anchors.centerIn: parent
             width: parent.width - (Kirigami.Units.largeSpacing * 4)
             visible: deviceConnected && view.count == 0 && currentSearchText.length != 0