fix: zig update build errors

src/app.zig

@@ -33,7 +33,7 @@ pub fn App(comptime E: type) type {
         // global variable for the registered handler for WINCH
         var handler_ctx: *anyopaque = undefined;
         /// registered WINCH handler to report resize events
-        fn handleWinch(_: c_int) callconv(.C) void {
+        fn handleWinch(_: c_int) callconv(.c) void {
             const this: *@This() = @ptrCast(@alignCast(handler_ctx));
             // NOTE this does not have to be done if in-band resize events are supported
             // -> the signal might not work correctly when hosting the application over ssh!