Change the way we distinguish client from server

[BohdanYavorskyi]

From @kkomelin :

Previous condition typeof process === 'undefined' that detected client stopped working when some frameworks started to misuse the process variable, so we need to find a better way to distinguish client from server.

Many libraries are using the typeof window !== 'undefined' condition to detect the client instead, and it's currently the best known way to do it, so let's switch to it.

Even though the change is more or less safe, we are planning to release a new major version to avoid breaking things.

[kkomelin]

Thank you @BohdanYavorskyi for your contribution.
It's an obvious change but still a bit risky, so I think we need to release it as a new major version. What do you think?

[BohdanYavorskyi]

Thank you @BohdanYavorskyi for your contribution. It's an obvious change but still a bit risky, so I think we need to release it as a new major version. What do you think?

yeah, can be major one

[kkomelin]

Thanks again @BohdanYavorskyi. I'm preparing for a new major release. However, I cannot guarantee that all people like it, and if I see a better solution, I can consider switching to it in the future. For now, we should be good.

[kkomelin]

Please test and let me know if you notice any issues https://github.com/kkomelin/isomorphic-dompurify/releases/tag/v2.0.0