Show which item in a listing is selected, even if the listing isn't selected

This is foundation for actively highlighting the result of a jump-to
while typing. (Since your focus is on the ListingJumpElement, there
needs to be some way to see which item would be selected in the
GrouplikeListing. That's what this commit implements.)

This also looks pretty nifty when you press M to open the context menu,
if I do say so myself.

1 files changed, 5 insertions, 0 deletions

diff --git a/todo.txt b/todo.txt
index 36eeb05..869b051 100644
--- a/todo.txt
+++ b/todo.txt
@@ -125,3 +125,8 @@ TODO: Entering more than one key "at once" into a text input element will only
       text. (This is an issue when pasting or spamming the keyboard.) Should be
       fixed in tui-lib.
       (Done!)
+
+TODO: Pressing space while an "Up (to <group>)" button is selected both
+      activates the button and pauses music (because the app detects that the
+      space key is pressed). This is definitely wrong (it should do one or the
+      other - I'm not too sure which, yet, but probably the latter).