Set expectation for example_nordvpnlite_config.json

[gindoslaw]

Add a small message for the nordvpnlite users.

Problem

example_nordvpnlite_config.json may be a temptation for a copy-paste. Settings are good for software engineers, but also are the trap for new users.

Solution

Add warning at the beginning of the file and point user to the alternative file used in OpenWRT package.

[nord-llt]

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[tomasz-grz]

Unfortunately JSON format does not support file comments.

And would also cause test_config_example to fail. which is there only to make sure the example config is updated and valid..

The main question is if we actually need example_nordvpnlite_config.json, maybe better documentation instead?