Add default language server for HTML

[David-Else]

Formatting now works after much experimentation.

Neovim provides these additional settings:

    init_options = {
      embeddedLanguages = { css = true, javascript = true },
      configurationSection = { 'html', 'css', 'javascript' },
    },

But I don't think they are doing anything extra in Helix. Without them it still seems to be accepting and formatting JS, I think it is best to leave them out for now unless someone else knows more about them.

I will add to the WIKI when this is merged.

[the-mikedavis]

looks good, thanks!