Refactor MFM

Co-authored-by: syuilo syuilotan@yahoo.co.jp

src/misc/extract-emojis.ts

@@ -0,0 +1,9 @@
+import { EmojiNode, MfmForest } from '../mfm/parser';
+import { preorderF } from '../prelude/tree';
+import { unique } from '../prelude/array';
+
+export default function(mfmForest: MfmForest): string[] {
+	const emojiNodes = preorderF(mfmForest).filter(x => x.type === 'emoji') as EmojiNode[];
+	const emojis = emojiNodes.filter(x => x.props.name && x.props.name.length <= 100).map(x => x.props.name);
+	return unique(emojis);
+}