Introduce config options for overview border: overview-active-border and overview-select-border

config.h

@@ -495,6 +495,8 @@ struct config {
             uint32_t active_bg;
             uint32_t active_fg;
             uint32_t unread_fg;
+            uint32_t overview_active_border;  /* ring around the currently-active tab in the overview */
+            uint32_t overview_select_border;  /* ring around keyboard/hover-selected tab in the overview */
         } colors;
     } tabs;
 

foot.ini

@@ -193,6 +193,8 @@ height=26
 # inherit-cwd=no         (new tabs open in the active tab's cwd; requires OSC 7 shell support)
 # unread-indicator=●     (string drawn before label when tab has unseen output; empty disables)
 # unread-color=fabd2f    (color of the unread-indicator)
+# overview-active-border=fabd2f  (ring around the currently-active tab in tab overview)
+# overview-select-border=ffffff  (ring around the keyboard/hover-selected tab in tab overview)
 
 [csd]
 # preferred=server