Implement a parser for the LSP and define T-Reqs grammar

User Story

As a developer I want to have a parser for T-Reqs syntax, so that the LSP can accurately analyse it and provide language features such as syntax highlighting, autocompletion, and diagnostics.

Traceability

• Related to: #
• T-Reqs ID:

Acceptance criteria

• The parser must correctly parse valid T-Reqs documents without errors.
• It should return a structured representation of the document.