install frida core from pip install frida-tools

[gogo2464]

I met a common issue where pip install frida-tools returns:

`ERROR: Command errored out with exit status 1

RuntimeError: Need frida-core devkit to build from source.
Download one from https://github.com/frida/frida/releases, extract it to a directory,
and then add an environment variable named FRIDA_CORE_DEVKIT pointing at the directory.

ERROR: Failed building wheel for frida
`

on windows 10 with python 3.8.0 installed from chocolatey.

It is not documented on https://frida.re/docs/troubleshooting/ but I suggest to modify the setup.py to install it by default if not installed yet.