Add len support for tree-sitter

[Ph0enixKM]

No description provided.

[lens0021]

I've noticed there are types of built-in:

• cd, echo and exit don't require parentheses.
• len and lines requires parentheses.
• nameof is categorized as an unop in some reason.
• mv requires two strings.

Does the len support mean built-in functions should be distinguished from normal functions by creating a new rule?