Allow lit 3

[alexgagnon]

What I did

1. Update peerDependencies to include Lit@3
2. Fix issue in packages/codelabs/src/intermediate/lit-html.md that was causing failures in prettier
3. Fix issue in `packages/dev-server-hmr/src/hmrPlugin.js that was causing failures in tsc
4. Provide files for testing against both Lit@2 and Lit@3

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🦋 Changeset detected

Latest commit: 556444f

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@open-wc/lit-helpers	Minor

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[Westbrook]

Do we actually need to vend multiple exports/add multiple hard dependencies, or can we just loosen this peerDependency to include ^2.0.0 || ^3.0.0 so that the consuming project can continue to outline the versions of the dependencies they need rather than forcing both versions that the change does now?

[alexgagnon]

sigh I switched laptops and forgot to put the only change that was actually needed... new commit updates the "peerDependencies", and I updated "dependencies" to "devDependencies"

[JosefJezek]

any progress? Why do you create the spread for lit 2, file spread-lit2.js?

[Westbrook]

This should have been fast forwarded as part of other changes. Can you check the latest versions?

[raphaelokon]

@Westbrook Do you need help on this topic? It is blocking us from updating to lit@3 …

[alexgagnon]

any progress? Why do you create the spread for lit 2, file spread-lit2.js?

spread-2.ts references lit@2 while spread.ts is updated for lit@3 so that both major versions can be tested.

I doesn't look like this has made it into upstream yet, and this is getting out of date. I'll close this and open another one with most recent changes

@Westbrook before I do... any issue with the current PR you'd want to see different? Is the testing against both Lit 2 and 3 the approach you want?

[tirithen]

What is holding up this pull request? Anything that can be done to speed it up a bit and merge? @Westbrook @alexgagnon

Can the scope of this pull request be reduced somehow to get build pipelines working for projects that want to upgrade to lit 3?