* Describe base code layout rules

* Enhance optional keyword explanation

* Change the logical operators description

* Document Range#to_set

* Update Thread#raise and Fiber#raise signatures and docs

* Add reference to String#strip to character_selectors.rdoc

* Update *nil docs when calling methods

* Enhance Array#find and #rfind docs

* Add a notice to Kernel#raise about cause:

Re-organize page docs

It was not documented as an operator that can be overriden, which is confusing because it makes you think it can't be.

Since https://github.com/ruby/ruby/pull/15212 these are proper syntax
errors, so no need to handle this explicitly anymore.

Also updated the example in the docs for this

removes documentation for the activation order of `include` and `prepend` inside a refinement