Rework Guide (#486)

* Move getting started to Guide

* Clean up summary and getting started

* Shorten intro by moving stuff to individual platform docs

* Make intro even shorter, summarize features

* Further cleanup; move development-related docs to separate section

* Make `guide` a crate. Turn code samples into examples so that we can check if they compile

* Rewrite "Describing the UI":

* Focus on RSX syntax (interactivity covered in later chapters); make sure samples are tested; concise language

* Move some "special attribute" samples to the `examples` directory

* Simplify introduction to components

* Simplify introduction to component props

* Document Prop features; add code samples

* Simplify component children docs

* Interactivity: better introduction to events

* Hooks: better introduction

* Remove outdated doc

* Introducs use_ref

* Simplify User Input chapter

* Document event handler props

* Meme editor example

* Meme editor walkthrough

* Add dark mode example

* Guide for context; dark mode example

* Guide: custom hooks

* Guide: conditional rendering

* Guide: rendering lists

* Guide: rendering lists + keys

* Move remaining infor from Reference to guide

* Delete reference book

docs/guide/examples/input_controlled.rs

@@ -0,0 +1,21 @@
+#![allow(non_snake_case)]
+use dioxus::prelude::*;
+
+fn main() {
+    dioxus::desktop::launch(App);
+}
+
+// ANCHOR: component
+fn App(cx: Scope) -> Element {
+    let name = use_state(&cx, || "bob".to_string());
+
+    cx.render(rsx! {
+        input {
+            // we tell the component what to render
+            value: "{name}",
+            // and what to do when the value changes
+            oninput: move |evt| name.set(evt.value.clone()),
+        }
+    })
+}
+// ANCHOR_END: component