Missing rule to make target 'install'

Created by: Legendacan

Hi, I've wanted to use cget to install your package to mine project

cget install bblanchon/ArduinoJson

Everything builds correctly but fails when exporting because it is missing install command for target it fails with this

make: *** No rule to make target 'install'.  Stop.
Command failed: ['/usr/bin/cmake', '--build', '/home/sajmon/Documents/projects/common/cget/cget/build/tmp-16109d5a253848be8b41c00b9603c06a/build', '--config', 'Release', '--target', 'install', '--', '-j', '12']
Failed to build package bblanchon/ArduinoJson

I've found you have install commands for tests, but not for package.

Can you add install to top-level cmake file please?