feat: add support for Lean

[ydewit]

Lean is a functional programming language and interactive theorem prover developed by Microsoft Research. It bridges the gap between automated and interactive theorem proving, supporting both mathematical reasoning and general-purpose programming.

Key features of Lean include:

• Dependent type theory
• Tactics for interactive theorem proving
• Metaprogramming capabilities
• Support for both functional programming and mathematical formalization

Here's a sample of Lean code to demonstrate the syntax:

import Mathlib.Tactic

-- Define a simple function
def double (n : Nat) : Nat := 2 * n

-- Prove a simple theorem
theorem double_zero : double 0 = 0 := by
  rw [double, Nat.mul_zero]

-- Define an inductive type
inductive Tree (α : Type)
  | leaf : α → Tree α
  | node : Tree α → Tree α → Tree α

-- Pattern matching on the Tree type
def treeSize {α : Type} : Tree α → Nat
  | Tree.leaf _ => 1
  | Tree.node l r => treeSize l + treeSize r + 1

-- Use a tactic block for a more complex proof
theorem treeSize_positive {α : Type} (t : Tree α) : treeSize t > 0 := by
  induction t with
  | leaf _ => simp [treeSize]; exact Nat.zero_lt_one
  | node l r ihl ihr => 
    simp [treeSize]
    exact Nat.lt_trans ihl (Nat.lt_add_right _ _ _)

#eval double 21  -- Evaluates to 42

[netlify[bot]]

✅ Deploy Preview for textmate-grammars-themes ready!

Name	Link
🔨 Latest commit	20e0e94a093d779340ad5d63321c1529b505d964
🔍 Latest deploy log	https://app.netlify.com/sites/textmate-grammars-themes/deploys/669026f575f4b20007b9e3b7
😎 Deploy Preview	https://deploy-preview-69--textmate-grammars-themes.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[ydewit]

I cannot see lean as part of the languages in the playground: https://deploy-preview-69--textmate-grammars-themes.netlify.app/ Although I could see it in my local playground.

[cireu]

hello, I'm using Shiki for Lean4 highlight and I found the line comment highlight is broken. Do you have any ideas?

(The picture is taken from https://shiki.style/)