Fixed notifications, updated borders and paddings

- Fixed notifications in GNOME 47 (likely Ubuntu) and older (Fixes #64);
- Fixed big margins between messages for GNOME 47 and older;
- Fixed margins in modal for GNOME 46 and oler;
- Adapted paddings and borders in quick settings and in screenshot panel;
- Changed styles in tooltips and popup messages;

theme/gnome-shell/.versions/48../.css/messages.css

@@ -0,0 +1,16 @@
+.message-view .message {
+	background-color: SECTION-OPAQUE-COLOR;
+	margin-bottom: 8px !important;
+}
+
+.message:second-in-stack {
+	background-color: SECTION-OPAQUE_SECOND;
+}
+
+.message:lower-in-stack {
+	background-color: SECTION-OPAQUE_THIRD;
+}
+
+.message-view .message:hover {
+	background-color: SECTION-OPAQUE_HOVER;
+}