stats.lua: allow keybindings to toggle the display of a specific page

This lets you define bindings like h script-binding
stats/display-page-4-toggle. Requested in #14966.

DOCS/interface-changes/display-page-toggle.txt

@@ -0,0 +1 @@
+add `display-page-n-toggle` script bindings to stats.lua, where n is a page number

DOCS/man/stats.rst

@@ -233,7 +233,7 @@ Additional keys can be configured in ``input.conf`` to display the stats::
 And to display a certain page directly::
 
     i script-binding stats/display-page-1
-    e script-binding stats/display-page-2
+    h script-binding stats/display-page-4-toggle
 
 Active key bindings page
 ~~~~~~~~~~~~~~~~~~~~~~~~

player/lua/stats.lua

@@ -1750,14 +1750,20 @@ mp.add_key_binding(nil, "display-stats", function() process_key_binding(true) en
 mp.add_key_binding(nil, "display-stats-toggle", function() process_key_binding(false) end,
     {repeatable=false})
 
--- Single invocation bindings without key, can be used in input.conf to create
--- bindings for a specific page: "e script-binding stats/display-page-2"
 for k, _ in pairs(pages) do
-    mp.add_key_binding(nil, "display-page-" .. k,
-        function()
+    -- Single invocation key bindings for specific pages, e.g.:
+    -- "e script-binding stats/display-page-2"
+    mp.add_key_binding(nil, "display-page-" .. k, function()
         curr_page = k
         process_key_binding(true)
     end, {repeatable=true})
+
+    -- Key bindings to toggle a specific page, e.g.:
+    -- "h script-binding stats/display-page-4-toggle".
+    mp.add_key_binding(nil, "display-page-" .. k .. "-toggle", function()
+        curr_page = k
+        process_key_binding(false)
+    end, {repeatable=true})
 end
 
 -- Reprint stats immediately when VO was reconfigured, only when toggled