Fix more examples to work with dioxus-native (#5179)

* Enable native for hotdog, file-explorer, and bluetooth-scanner examples

Signed-off-by: Nico Burns <nico@nicoburns.com>

* Fix crash in calculator example

Signed-off-by: Nico Burns <nico@nicoburns.com>

* Add config macro for native

* Add Config struct to dioxus-native

* Re-export dioxus-native as dioxus::native

* Fix calculator example to work with dioxus-native

* Fix calculator_mutable example to work with dioxus-native

---------

Signed-off-by: Nico Burns <nico@nicoburns.com>

examples/01-app-demos/calculator.rs

@@ -12,15 +12,24 @@ use dioxus::events::*;
 use dioxus::html::input_data::keyboard_types::Key;
 use dioxus::prelude::*;
 
+const TITLE: &str = "Calculator";
 const STYLE: Asset = asset!("/examples/assets/calculator.css");
 
 fn main() {
-    dioxus::LaunchBuilder::desktop()
+    dioxus::LaunchBuilder::new()
         .with_cfg(desktop!({
             use dioxus::desktop::{Config, LogicalSize, WindowBuilder};
             Config::new().with_window(
                 WindowBuilder::default()
-                    .with_title("Calculator")
+                    .with_title(TITLE)
+                    .with_inner_size(LogicalSize::new(300.0, 525.0)),
+            )
+        }))
+        .with_cfg(native!({
+            use dioxus::native::{Config, LogicalSize, WindowAttributes};
+            Config::new().with_window_attributes(
+                WindowAttributes::default()
+                    .with_title(TITLE)
                     .with_inner_size(LogicalSize::new(300.0, 525.0)),
             )
         }))
@@ -146,7 +155,7 @@ fn calc_val(val: &str) -> f64 {
     let mut temp_value;
     let mut fin_index = 0;
 
-    if &val[0..1] == "-" {
+    if val.len() > 1 && &val[0..1] == "-" {
         temp_value = String::from("-");
         fin_index = 1;
         start_index += 1;