[Emmet] per-language "Trigger expansion on tab"

<!-- ⚠️⚠️ Do Not Delete This! feature_request_template ⚠️⚠️ --> <!-- Please read our Rules of Conduct: https://opensource.microsoft.com/codeofconduct/ --> <!-- Please search existing issues to avoid creating duplicates. --> <!-- Describe the feature you'd like. --> Using tab to complete an element is useful in HTML, but ends up causing a lot of false triggers in JS and TS. I do want emmet in JS in general, but only in the suggestions list and not just when I press tab anywhere. I tried to enable the setting for only HTML files but the setting was not available on a per-language basis.