add course - Kotlin for Java Developers by Jetbrains

[Delebrith]

What does this PR do?

Add resource on Kotlin (course by Svetlana Isakova & Andrey Breslav, Jetbrains)

For resources

Description

Course covers all the knowledge necessary for Java developers to switch to Kotlin and work in that language effectively.

Why is this valuable (or not)?

Course is divided in chapters covering different parts of Kotlin language features. It provides insight into differences and similarities between Kotlin and Java. It has many questions in between lessons and lots of practical exercises and even mini-projects.

How do we know it's really free?

Coursera badge promises it (and I've done it 4 free 😉 )

For book lists, is it a book? For course lists, is it a course? etc.

It is a course.

Checklist:

• [x] Read our contributing guidelines.
• [x] Search for duplicates.
• [x] Include author(s) and platform where appropriate.
• [x] Put lists in alphabetical order, correct spacing.
• [x] Add needed indications (PDF, access notes, under construction).
• [x] Used an informative name for this pull request.

Follow-up

• Check the status of GitHub Actions and resolve any reported warnings!