Rename modules to use snake_case (#1498)

packages/hooks/src/use_collection.rs

@@ -0,0 +1,76 @@
+/*
+a form of use_state explicitly for map-style collections (BTreeMap, HashMap, etc).
+
+Why?
+---
+Traditionally, it's possible to use the "use_state" hook for collections in the React world.
+Adding a new entry would look something similar to:
+
+```js
+let (map, set_map) = useState({});
+set_map({ ...map, [key]: value });
+```
+The new value then causes the appropriate update when passed into children.
+
+This is moderately efficient because the fields of the map are moved, but the data itself is not cloned.
+However, if you used similar approach with Dioxus:
+
+```rust
+let (map, set_map) = use_state(cx, || HashMap::new());
+set_map({
+    let mut newmap = map.clone();
+    newmap.set(key, value);
+    newmap
+})
+```
+Unfortunately, you'd be cloning the entire state every time a value is changed. The obvious solution is to
+wrap every element in the HashMap with an Rc. That way, cloning the HashMap is on par with its JS equivalent.
+
+Fortunately, we can make this operation even more efficient in Dioxus, leveraging the borrow rules of Rust.
+
+This hook provides a memoized collection, memoized setters, and memoized getters. This particular hook is
+extremely powerful for implementing lists and supporting core state management needs for small apps.
+
+If you need something even more powerful, check out the dedicated atomic state management Dioxus Dataflow, which
+uses the same memoization on top of the use_context API.
+
+Here's a fully-functional todo app using the use_map API:
+```rust
+static TodoList: Component = |cx| {
+    let todos = use_map(cx, || HashMap::new());
+    let input = use_ref(|| None);
+
+    cx.render(rsx!{
+        div {
+            button {
+                "Add todo"
+                onclick: move |_| {
+                    let new_todo = TodoItem::new(input.contents());
+                    todos.insert(new_todo.id.clone(), new_todo);
+                    input.clear();
+                }
+            }
+            button {
+                "Clear todos"
+                onclick: move |_| todos.clear()
+            }
+            input {
+                placeholder: "What needs to be done?"
+                ref: input
+            }
+            ul {
+                {todos.iter().map(|todo| rsx!(
+                    li {
+                        key: todo.id
+                        span { "{todo.content}" }
+                        button {"x", onclick: move |_| todos.remove(todo.key.clone())}
+                    }
+                ))}
+            }
+        }
+    })
+}
+
+```
+
+*/