Add Rust and C++ linked list implementations with build/debug configs

Rust version in src/main.rs (Cargo project) and a C++ port in cpp/main.cpp
using raw pointers, both with VS Code build tasks and gdb-based debug
configs. Vendors vscode-debug-visualizer and visualization as submodules
for reference while building a custom node-table graph visualizer.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/main.rs

@@ -0,0 +1,57 @@
+// A single node containing data and an optional pointer to the next node
+struct Node<T> {
+    data: T,
+    next: Option<Box<Node<T>>>,
+}
+
+// The main wrapper for the linked list tracking the head node
+pub struct LinkedList<T> {
+    head: Option<Box<Node<T>>>,
+}
+
+impl<T> LinkedList<T> {
+    // Create an empty linked list
+    pub fn new() -> Self {
+        LinkedList { head: None }
+    }
+
+    // Add a new element to the front of the list
+    pub fn push_front(&mut self, data: T) {
+        let new_node = Box::new(Node {
+            data,
+            // .take() temporarily leaves None in self.head and extracts the value
+            next: self.head.take(), 
+        });
+        self.head = Some(new_node);
+    }
+
+    // Remove and return the front element of the list
+    pub fn pop_front(&mut self) -> Option<T> {
+        self.head.take().map(|node| {
+            self.head = node.next;
+            node.data
+        })
+    }
+
+    // Read the front element without removing it
+    pub fn peek_front(&self) -> Option<&T> {
+        self.head.as_ref().map(|node| &node.data)
+    }
+}
+
+fn main() {
+    let mut list = LinkedList::new();
+
+    // Demonstrate pushing items
+    list.push_front(10);
+    list.push_front(20);
+    list.push_front(30);
+
+    // Demonstrate peaking at the top item
+    println!("Top element: {:?}", list.peek_front()); // Output: Some(30)
+
+    // Demonstrate popping items
+    while let Some(value) = list.pop_front() {
+        println!("Popped: {}", value);
+    }
+}