Customize prompt selection colors

Seems like if we make the foreground color configurable, the selection
isn't colored at all?!

doc/help/settings.asciidoc

@@ -269,6 +269,7 @@
 |<<colors-messages.border.info,messages.border.info>>|Border color of an info message.
 |<<colors-prompts.fg,prompts.fg>>|Foreground color for prompts.
 |<<colors-prompts.bg,prompts.bg>>|Background color for prompts.
+|<<colors-prompts.selected.bg,prompts.selected.bg>>|Background color for the selected item in filename prompts.
 |==============
 
 .Quick reference for section ``fonts''
@@ -2192,6 +2193,12 @@ Background color for prompts.
 
 Default: +pass:[darkblue]+
 
+[[colors-prompts.selected.bg]]
+=== prompts.selected.bg
+Background color for the selected item in filename prompts.
+
+Default: +pass:[#308cc6]+
+
 == fonts
 Fonts used for the UI, with optional style/weight/size.
 

qutebrowser/config/configdata.py

@@ -1310,6 +1310,10 @@ def data(readonly=False):
              SettingValue(typ.QssColor(), 'darkblue'),
              "Background color for prompts."),
 
+            ('prompts.selected.bg',
+             SettingValue(typ.QssColor(), '#308cc6'),
+             "Background color for the selected item in filename prompts."),
+
             readonly=readonly
         )),
 

qutebrowser/mainwindow/prompt.py

@@ -244,6 +244,14 @@ class PromptContainer(QWidget):
             color: {{ color['prompts.fg'] }};
             background-color: {{ color['prompts.bg'] }};
         }
+
+        QTreeView {
+            selection-background-color: {{ color['prompts.selected.bg'] }};
+        }
+
+        QTreeView::item:selected, QTreeView::item:selected:hover {
+            background-color: {{ color['prompts.selected.bg'] }};
+        }
     """
     update_geometry = pyqtSignal()