feat request: add basic real language interpretation

[vanilla-extracts]

Implementing a real programming language to mini-calc.
Maybe functional ? Rust-like ?

• Conditions
  • If
  • If/else
• Flow-control
  • For
  • While
• Improving function declaration (with parameters and body)
• Implementing that into the interpreter
• Add a REPL command to execute a file
• Add a non-interactive command to execute a file