Add use_on_mount and fix some typos (#1497)

* Add `use_on_mount` and fix some typos

* Optimize away UseOnMount struct

* `use_on_mount`, `use_on_unmount` -> `use_on_create`, `use_on_destroy`

* Make `use_on_unmount` deprecated

---------

Co-authored-by: Evan Almloff <evanalmloff@gmail.com>

packages/hooks/src/use_on_create.rs

@@ -0,0 +1,27 @@
+use dioxus_core::ScopeState;
+use std::cell::Cell;
+use std::future::Future;
+
+/// A hook that runs a future when the component is mounted.
+///
+/// This is just [`use_effect`](crate::use_effect), but with no dependencies.
+/// If you have no dependencies, it's recommended to use this, not just because it's more readable,
+/// but also because it's a tiny bit more efficient.
+pub fn use_on_create<T, F>(cx: &ScopeState, future: impl FnOnce() -> F)
+where
+    T: 'static,
+    F: Future<Output = T> + 'static,
+{
+    let needs_regen = cx.use_hook(|| Cell::new(true));
+
+    if needs_regen.get() {
+        // We don't need regen anymore
+        needs_regen.set(false);
+
+        let fut = future();
+
+        cx.push_future(async move {
+            fut.await;
+        });
+    }
+}