(Doc+) link video for resolving shards too large

👋 howdy, team (cc: @anniegale9538 )! 

Playing forward #111254, [this video](https://www.youtube.com/watch?v=sHyNYnwbYro) demonstrates an example resolving shards too large via reindex under [this section](https://www.elastic.co/guide/en/elasticsearch/reference/master/size-your-shards.html#shard-size-recommendation) as it's a top support ask.

docs/reference/how-to/size-your-shards.asciidoc

@@ -208,6 +208,8 @@ index can be <<indices-delete-index,removed>>. You may then consider setting
 <<indices-add-alias,Create Alias>> against the destination index for the source 
 index's name to point to it for continuity. 
 
+See link:https://www.youtube.com/watch?v=sHyNYnwbYro[this video] for example
+troubleshooting walkthrough.
 
 [discrete]
 [[shard-count-recommendation]]