Add new MFM syntax

src/mfm/parse/elements/motion.ts

@@ -0,0 +1,20 @@
+/**
+ * Motion
+ */
+
+export type TextElementMotion = {
+	type: 'motion'
+	content: string
+	motion: string
+};
+
+export default function(text: string) {
+	const match = text.match(/^\(\(\((.+?)\)\)\)/);
+	if (!match) return null;
+	const motion = match[0];
+	return {
+		type: 'motion',
+		content: motion,
+		motion: match[1]
+	} as TextElementMotion;
+}