feat(exercise): really basic longest palindrome in text

src/exercises/medium.rs

@@ -0,0 +1,23 @@
+pub fn longest_palindrome(value: &str) -> String {
+    let mut lp: String = "0".to_string();
+    let input_size = value.len() - 1;
+
+    for pal_size in 2..=input_size {
+        for i in 0..input_size {
+            if input_size - i < pal_size {
+                break;
+            }
+            if let Some(slice) = value.get(i..(i + pal_size - 1)) {
+                // let reverted_slice = slice.chars().rev().collect::<String>();
+                // if string was mutable, we count use .reserve()
+                let reverted_slice = slice.chars().rev().collect::<String>();
+                if slice == reverted_slice {
+                    lp = reverted_slice;
+                    break;
+                }
+            }
+        }
+    }
+
+    lp
+}