Escher has been repurposed to be a metapackage around Interact.jl and other packages for web deployment (so far it includes Mux.jl but more things may be added as they become available). Refer to the Interact documentation (in particular the deployment section).
You can replace using Interact, Mux with using Escher, i.e.:
using Escher
ui = @manipulate for i in 1:100
i
end
webio_serve(page("/", req -> ui))