fix(dialog): pub export `Dialog`

fixes #2107

.changes/fix-dialog-export-dialog.md

@@ -0,0 +1,5 @@
+---
+dialog: patch
+---
+
+The `Dialog` struct is now correctly exported, primarily to fix the documentation on `docs.rs`.

plugins/dialog/src/lib.rs

@@ -39,6 +39,11 @@ use desktop::*;
 #[cfg(mobile)]
 use mobile::*;
 
+#[cfg(desktop)]
+pub use desktop::Dialog;
+#[cfg(mobile)]
+pub use mobile::Dialog;
+
 pub(crate) const OK: &str = "Ok";
 pub(crate) const CANCEL: &str = "Cancel";
 pub(crate) const YES: &str = "Yes";