Add typescript integration to sapper template repo

[andrewragy]

Is your feature request related to a problem? Please describe.
As Svelte now supports typescript, please to integrate easy typescript for sapper

Describe the solution you'd like
add a script to the sapper template repos that automatically that turns the project to typescript like with the svelte template.

Describe alternatives you've considered
none

How important is this feature to you?
Very important! It will encourage me to work on more sapper projects

[Conduitry]

It doesn't fully work yet. #760