Typo in install instructions, causes rules to be written to /rules.d

[lbeltrame]

Describe the bug

The pkg-config invocation should be:

pkg-config --variable=udevdir udev

Otherwise, at least on my openSUSE system, I get

pkg-config --variable=udev
Please specify at least one package name on the command line.

This causes the udev rules to be written to /rules.d because the subprocess does not return any output.

To Reproduce
Steps to reproduce the behavior:

1. Execute the configure call in INSTALL.md

[nirenjan]

Thanks for the bug report. I've fixed it in the master branch. Please reopen if you still have issues.