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

[arthurevans]

#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.

[busynest]

This makes everything work

      <!-- Force Polyfills -->
      <script
        async
        Set-Cookie: polyr=poly; SameSite=Lax>
          // Force Polyfills
          if (window.customElements) window.customElements.forcePolyfill = true;
          ShadyDOM = { force: true };
          ShadyCSS = { shimcssproperties: true};
      </script>

[justinfagnani]

I vote for (1) also