Extend the feature modeling language with XOR, OR and Optionality

[sidrasali]

Description

This PR extends the feature model editor's syntax to support OR/XOR grouping and feature optionality in the HAnS plugin. We added new tokens to the grammar and updated the lexer to recognize these tokens. Due to time issues and difficulties with another task, the implementation is not complete and might not be fully correct.

Related Issue

#42

Motivation and Context

These capabilities bring HAnS's feature modeling closer to CLAFER standard and improve expressiveness of feature models.

How Has This Been Tested?

• Tests are created and passing
• Manual testing

Demo:

Screen.Recording.2025-02-28.at.23.12.36.mov

Types of changes

• Pipeline changes
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
  • I have updated the documentation accordingly.
• I have updated the CONTRIBUTORS file.
• I have updated the CHANGELOG.