added pointer dereference example

ptr-deref/Cargo.toml

+[package]
+name = "ptr-deref"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

ptr-deref/src/main.rs

+fn main() {
+    // First create a `Vec`
+    let mut vec = Vec::from([100, 101, 102]);
+
+    // Let's take a raw pointer to the first item
+    let ptr0 = &raw mut vec[0];
+
+    // Also a raw pointer to the second item
+    let ptr1 = unsafe { ptr0.add(1) };
+
+    // Here I am implicitly taking a mutable reference to `vec`
+    vec[0] = 300;
+
+    // Unsafe but valid: no other reference at this point refers to
+    // memory overlapping *ptr1.
+    unsafe { *ptr1 = 301 };
+
+    // Valid: there is no mutable reference to memory owned by `vec`.
+    println!("OUTPUT: {:?}", &vec)
+}
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