feat: ✨ Add Share extension

app/extensions/share/page.mdx

@@ -0,0 +1,48 @@
+export const metadata = {
+    title: "Share Extension",
+    description: "Share Extension lets users share notes they like with others.",
+}
+
+# Share Extension
+
+The Share Extension lets users share notes they like with others. This is the same as Twitter's "retweet" and Mastodon's "boost". {{ className: 'lead' }}
+
+## Behaviour
+
+When a user shares a note, the note's original author **must** receive the entity alongside the user's followers. In clients, `Shares` should be rendered in a way that makes it clear that the shared note was originally authored by someone else than the user who shared it.
+
+`Shares` can be undone ("unboosting") with a [Delete](/entities/delete) entity.
+
+## Entity Definition
+
+<Row>
+    <Col>
+        <Properties>
+            <Property name="extension_type" type="string" required={true}>
+                Must be `pub.versia:share/Share`.
+            </Property>
+            <Property name="author" type="URI" required={true} typeLink="/types#uri">
+                Creator of the Share.
+            </Property>
+            <Property name="shared" type="URI" required={true} typeLink="/types#uri">
+                URI of the note being shared. Must link to a [Note](/entities/note).
+            </Property>
+        </Properties>
+    </Col>
+
+    <Col sticky>
+
+    ```jsonc {{ 'title': 'Example Share' }}
+    {
+        "id": "3e7e4750-afd4-4d99-a256-02f0710a0520",
+        "type": "Extension",
+        "extension_type": "pub.versia:share/Share",
+        "created_at": "2021-01-01T00:00:00.000Z",
+        "author": "https://example.com/users/6e0204a2-746c-4972-8602-c4f37fc63bbe",
+        "uri": "https://example.com/shares/3e7e4750-afd4-4d99-a256-02f0710a0520",
+        "shared": "https://otherexample.org/notes/fmKZ763jzIU8"
+    }
+    ```
+
+    </Col>
+</Row>

components/Navigation.tsx

@@ -289,6 +289,7 @@ export const navigation: NavGroup[] = [
         links: [
             { title: "Custom Emojis", href: "/extensions/custom-emojis" },
             { title: "Likes", href: "/extensions/likes" },
+            { title: "Share", href: "/extensions/share" },
             { title: "Vanity", href: "/extensions/vanity" },
             { title: "WebSockets", href: "/extensions/websockets" },
         ],