Do not translate example.com when writing translations

[reinhart1010]

Hi, as I found myself while preparing #15497, there may be cases of the example web domain example.com (as in placeholders) being translated in other languages.

While this mistake seems tolerable at a glance, doing so may put a potential security risk where a specific translation of example.com could resolve to a real web domain with unknown or malicious intentions. The real example.com, however, is solely reserved for IANA for documentation purposes, so it would still be safe for use for our technical documentation, as close to its original purpose.

So I would suggest to refrain translating example.com at least by our style guide, technically putting the term in a similar treatment with our stdin/stdout policy. Note that this does not apply to other kinds of network/internet/URI-related placeholders such as {{host}}:{{port}}.