doc: generate browsable API documentation

[HotFazz]

Description

Generate up to date browsable API documentation for the project using Javadoc and HTML.

Expected outcome

API documentation is generated automatically in a browsable HTML format and reflects the current state of the codebase.

Acceptance criteria

• The browsable documentation is based on Javadoc and HTML
• Documentation generation supports mvn javadoc:javadoc
• docs/index.html (or equivalent) is browsable in a browser
• Documentation is up to date with the codebase
• Statement of contribution is added on the repository root

Related

• How to write good API documentation