add a tutorial chapter

Author: Rich-Harris

site/content/tutorial/06-bindings/08-contenteditable-bindings/app-a/App.svelte

@@ -0,0 +1,15 @@
+<script>
+	let html = '<p>Write some text!</p>';
+</script>
+
+<div contenteditable="true"></div>
+
+<pre>{html}</pre>
+
+<style>
+	[contenteditable] {
+		padding: 0.5em;
+		border: 1px solid #eee;
+		border-radius: 4px;
+	}
+</style>

site/content/tutorial/06-bindings/08-contenteditable-bindings/app-b/App.svelte

@@ -0,0 +1,18 @@
+<script>
+	let html = '<p>Write some text!</p>';
+</script>
+
+<div
+	contenteditable="true"
+	bind:innerHTML={html}
+></div>
+
+<pre>{html}</pre>
+
+<style>
+	[contenteditable] {
+		padding: 0.5em;
+		border: 1px solid #eee;
+		border-radius: 4px;
+	}
+</style>

site/content/tutorial/06-bindings/08-contenteditable-bindings/text.md

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+---
+title: Contenteditable bindings
+---
+
+Elements with a `contenteditable="true"` attribute support `textContent` and `innerHTML` bindings:
+
+```html
+<div
+	contenteditable="true"
+	bind:innerHTML={html}
+></div>
+```