Add Download Last Version Direct Link (#62)

* Add Download Link

Download the last version of the RevitLookup.

* Update README.md
4 jobs for master in 5 minutes and 54 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Download Revit Api
passed #772477362
download-revit-api

00:00:19

 
  Build
passed #772477364
windows-1809 windows shared-windows
build

00:04:23

 
  Sign
passed #772477366
sign

00:00:32

 
  Publish
passed #772477367
publish

00:00:38