core: hook up the codepoint map to the loaded font group

src/Surface.zig

@@ -224,6 +224,11 @@ pub fn init(
         var group = try font.Group.init(alloc, font_lib, font_size);
         errdefer group.deinit();
 
+        // If we have codepoint mappings, set those.
+        if (config.@"font-codepoint-map".map.list.len > 0) {
+            group.codepoint_map = config.@"font-codepoint-map".map;
+        }
+
         // Search for fonts
         if (font.Discover != void) discover: {
             const disco = try app.fontDiscover() orelse {

src/config/Config.zig

@@ -104,6 +104,9 @@ const c = @cImport({
 ///
 /// This configuration can be repeated multiple times to specify multiple
 /// codepoint mappings.
+///
+/// Changing this configuration at runtime will only affect new terminals,
+/// i.e. new windows, tabs, etc.
 @"font-codepoint-map": RepeatableCodepointMap = .{},
 
 /// Draw fonts with a thicker stroke, if supported. This is only supported