The dev error for duplicate keys in a keyed each should identify which key is a duplicate #8410
Description
Describe the problem
#4301 added the very useful dev guard against duplicate keys in a keyed each block. However, it doesn't tell you which key is a duplicate
Reproduction: https://svelte.dev/repl/20dad117a77140baba233747864325ee?version=3.57.0
Describe the proposed solution
Emit the duplicate key as part of the error message
Alternatives considered
None, really.
Importance
would make my life easier