Improve publish instructions

[aslakhellesoy]

The old instructions for activating publishing allowed too many things to go wrong:

• Many users don't know how to set environment variables. They'll set them in Windows system settings not realising a reboot is required to make it take effect
• Adding publish = true to @CucumberOptions will have no effect if Cucumber is run from IDEA's native runner (green triangles in the gutter)

For this reason the top recommendation is now to set cucumber.publish.enabled=true in src/test/resources/cucumber.properties. This should be picked up regardless of how people run Cucumber.

I've also removed the recommendation to use src/test/resources/junit-platform.properties since it will be ignored when using the IDEA runner.

[coveralls]

Coverage remained the same at 86.178% when pulling 080d40c on improve-publish-instructions into bba8cc9 on main.

[mpkorstanje]

I've also removed the recommendation to use src/test/resources/junit-platform.properties since it will be ignored when using the IDEA runner.

It depends how you launch the tests. If you launch tests in IDEA via JUnit 5 and you are using cucumber-junit-platform-engine then it will use the junit-platform.properties. For example if you run all tests in a package it will use JUnit 5. And I've got a feature request with IDEA to use JUnit 5 rather then the CLI when selecting a feature files https://youtrack.jetbrains.com/issue/IDEA-227508