Simple plug to just fallback to the index.html file

IndexFallbackPlug.ex

defmodule Karta.Web.ReactPlug do
  import Plug.Conn

  def init(options), do: options

  def call(conn, _opts) do
    conn
    |> put_resp_header("content-type", "text/html; charset=utf-8")
    |> Plug.Conn.send_file(200, Application.app_dir(:karta_web, "priv/static/index.html"))
  end
end