[lit-starter-*] starter kits require `override` which isn't documented

#2060 enabled `noImplicitOverride` in all of the `lit` monorepo, including the starter kit projects.

The examples on the doc site don't use the `override` keyword, which means you can't copy/paste them into a starter kit project.

We should either 1) roll this change back for the starter kits, or 2) update all of the sample code on the site.

I vote for #1, personally.

Review the noImplicitOverride change from #2060 and inspect the starter kit projects alongside the doc-site sample code. Decide whether starter kits should avoid this requirement or whether all samples should be updated; done means copied examples work in the starter kits and the chosen behavior is consistent.

Written by the indexing model from the issue text.