snapshot is produced with non-unique IDs #76
Description
In some cases calling snapshot(document) produces a tree with elements which IDs are not unique. In most cases these elements are the root element document and the first element from <head> e.g. <link> or <style>.
It leads to the situation where in Player the root element document with id = 1 is overwritten by some child node, that also has id = 1. In this case IncrementalSource.Event, which is fired for document, won't be correctly processed by the Player instance.
Here the assignment of non-unique IDs happen:
https://github.com/rrweb-io/rrweb-snapshot/blob/master/src/snapshot.ts#L693