Add an option to validate to force keyed each instead of allowing both

[dtzxporter]

Describe the problem

Vue required that all looped blocks specify a key and it makes it easier to work with and less likely to run into an issue later.

Describe the proposed solution

It would be nice to have a lint option that would error when compiling a each block that isn't keyed.

Alternatives considered

N/A

Importance

would make my life easier

[bluwy]

I think this should live in eslint rather than being built into the Svelte compiler. There's a similar closed issue there, and I agree with the consensus that there are cases where keyed each blocks aren't always needed.

[alex-k-exe]

I think this issue should be labeled as stale

[Conduitry]

I'm going to close this. I don't think this is something that we should push people towards - nor something that we present as an option for people to push themselves toward.