Global CLI Required

Currently Ionic requires a bunch of things to be installed globally.
This pattern seems to be very error prone and counter productive.

I run a consultancy company that deals with multiple applications at once running different versions of Ionic (3, 4, 5).
Depending on the version of the CLI you need different dependencies (cordova-res, native-run, cordova, ...).

Ionic should install these dependencies locally so developers can use `npx ` without requiring ANY globally installed packages.

This already currently works to a certain degree, i have an Ionic 3 and 4 project that have everything installed locally and work fine.

This should be the accepted pattern going forward though in order to make this framework more future proof and less frustrating for devs needing to support multiple applications running multiple versions.

Start by reviewing how the Ionic CLI resolves and installs dependencies for projects, especially the commands currently expected to be installed globally. Compare that behavior with the locally installed Ionic 3 and 4 projects described in the issue. Done means supported Ionic projects can invoke required commands through npx without any globally installed packages.

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