More Robust 3.x to 4.x documentation

Thank you for your suggestion.

The dev doc has more info for upgrading. If you don't see it, check it out.
https://codeigniter4.github.io/CodeIgnit...ading.html

And it would be great to inform what is missing.

Whoa, I don't know how I missed this. I had only seen this: https://codeigniter.com/user_guide/insta...e_4xx.html

Perhaps a link to https://codeigniter4.github.io/CodeIgnit...ading.html could be added to that page in case others do like I did and look at what I did and then stop searching thinking that is the definitive guide.

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If there are things missing, should I post them in this thread or create an issue in Github?