Please improve documentation related to Java 11 requirements

[JavaJimFl]

Is your feature request related to a problem? Please describe.**

Upgrading the plugin to v2.0.2 causes analysis failures with SonarQube scanners older than version 4.0 because the plugin is compiled with Java 11 and the v3.x of the SonarQube Scanner has a v1.8 embedded JRE.

Describe the solution you'd like

Update the documentation and release notes to indicate that a Java 11 JRE is required to use the plugin, not just that the plugin supports Java 11.

Describe alternatives you've considered

A clear and concise description of any alternative solutions or features you've considered.

Additional context

Add any other context or screenshots about the feature request here.

[JavaJimFl]

After a couple of attempts to upgrade the plugin to v2.0.2, I finally had to roll back to v2.0.1. Our original symptom appeared to be limited to the command line scanner with it's embedded JRE, but we've found Maven and Gradle builds failing because the build tools themselves use a Java 8 JDK. We have dozens of build servers across multiple business units, so we have no idea what JDKs are being used because we don't own them.

This upgrade should have come with a big warning label or have been released a major version because the change is so drastic. :)

[Vermyndax]

Having this issue as well on 2.0.2

[JackFish]

can we have a java8 version for this plugin? Our project build has blocked by this version 2.0.2.