Use `move` closures in filter callback examples

Trying to capture values by ref won't work for anything that's
not `'static`

ctru-rs/examples/software-keyboard.rs

@@ -19,7 +19,7 @@ fn main() {
     // Custom filter callback to handle the given input.
     // Using this callback it's possible to integrate the applet
     // with custom error messages when the input is incorrect.
-    keyboard.set_filter_callback(Some(Box::new(|str| {
+    keyboard.set_filter_callback(Some(Box::new(move |str| {
         if str.contains("boo") {
             return (CallbackResult::Retry, Some("Ah, you scared me!".into()));
         }

ctru-rs/src/applets/swkbd.rs

@@ -348,7 +348,7 @@ impl SoftwareKeyboard {
     ///
     /// let mut keyboard = SoftwareKeyboard::default();
     ///
-    /// keyboard.set_filter_callback(Some(Box::new(|str| {
+    /// keyboard.set_filter_callback(Some(Box::new(move |str| {
     ///     if str.contains("boo") {
     ///         return (CallbackResult::Retry, Some("Ah, you scared me!".into()));
     ///     }