refactor(ui): extract virtual-follow-list for message stream

packages/ui/src/components/message-anchors.ts

@@ -0,0 +1,9 @@
+export const MESSAGE_ANCHOR_PREFIX = "message-anchor-"
+
+export function getMessageAnchorId(messageId: string) {
+  return `${MESSAGE_ANCHOR_PREFIX}${messageId}`
+}
+
+export function getMessageIdFromAnchorId(anchorId: string) {
+  return anchorId.startsWith(MESSAGE_ANCHOR_PREFIX) ? anchorId.slice(MESSAGE_ANCHOR_PREFIX.length) : anchorId
+}