feat: support paste html

example/assets/example.html

@@ -0,0 +1,49 @@
+<h1>AppFlowyEditor</h1>
+<h2>👋 <strong>Welcome to</strong> <strong><em><a href="appflowy.io">AppFlowy Editor</a></em></strong></h2>
+  <p>AppFlowy Editor is a <strong>highly customizable</strong> <em>rich-text editor</em></p>
+
+<hr />
+
+<p><u>Here</u> is an example <del>your</del> you can give a try</p>
+
+<span style="font-weight: bold;background-color: #cccccc;font-style: italic;">Span element</span>
+
+<span style="font-weight: medium;text-decoration: underline;">Span element two</span>
+
+<span style="font-weight: 900;text-decoration: line-through;">Span element three</span>
+
+<a href="https://appflowy.io">This is an anchor tag!</a>
+
+<img src="https://images.squarespace-cdn.com/content/v1/617f6f16b877c06711e87373/c3f23723-37f4-44d7-9c5d-6e2a53064ae7/Asset+10.png?format=1500w" />
+
+<h3>Features!</h3>
+
+<ul>
+  <li>[x] Customizable</li>
+  <li>[x] Test-covered</li>
+  <li>[ ] more to come!</li>
+</ul>
+
+<ol>
+  <li>First item</li>
+  <li>Second item</li>
+</ol>
+
+<li>List element</li>
+
+<blockquote>
+  <p>This is a quote!</p>
+</blockquote>
+
+<code>
+  Code block
+</code>
+
+<em>Italic one</em> <i>Italic two</i>
+
+<b>Bold tag</b>
+<img src="http://appflowy.io" alt="AppFlowy">
+<p>You can also use <strong><em>AppFlowy Editor</em></strong> as a component to build your own app.</p>
+<h3>Awesome features</h3>
+<p>If you have questions or feedback, please submit an issue on Github or join the community along with 1000+ builders!</p>
+