Upgrade README to require at least JDK 17

[Avanatiker]

This change updates the project's requirements to mandate at least JDK 17. The primary reason is compatibility with the intellij-platform-gradle-plugin version 2.0.1, which is built for Java 17.

Attempts to resolve dependencies with Java 11 fail due to compatibility issues, as the plugin's apiElements and runtimeElements require Java 17. Additionally, Gradle features used by the plugin, such as org.gradle.plugin.api-version=8.6, further necessitate upgrading the JDK.

[JojOatXGME]

Thanks for your contribution. You indeed need Java 17 to build the project. We even use Java 17 ourselves, not only for dependencies.

Anyway, there seems to be some problem with the build. Shouldn't have anything to do with your changes. 😄 Here is a link to the build. I am wondering if the error is caused by gradle/actions/setup-gradle@v3. I switched to this action earlier this year. I will take a look.

FAILURE: Build failed with an exception.

* Where:
Initialization script '/home/runner/work/_temp/dummy-cleanup-project/init.gradle' line: 8

* What went wrong:
Cannot get the value of write-only property 'removeUnusedEntriesOlderThan' for object of type org.gradle.api.internal.cache.DefaultCacheConfigurations$DefaultCacheResourceConfiguration.

[JojOatXGME]

I have fixed the issue with the build in 64602c0. I also rebased your PR to make the build work. Afterward, I realized that rebasing the branch of someone else's PR is probably not the wisest action 😅.

I would merge the PR if you don't have any objections.

[Avanatiker]

Haha its ok! Also looks good to me 🐱 start the merge 🚂 ❄️