Add Trapping Rainwater problem implementation (Two Pointer Approach) (#6990)

* Add Trapping Rainwater problem implementation (Two Pointer Approach)

* Add Wikipedia reference link for Trapping Rainwater problem

* fix: format TrappingRainwater.java for CI check

* fix: add package and resolve checkstyle errors for TrappingRainwater.java

* fix: declare TrappingRainwater as final to pass Checkstyle

* Add test cases for TrappingRainwater algorithm

* Add test cases for TrappingRainwater algorithm

* Move TrappingRainwater algorithm to stacks package

* Fix: Move TrappingRainwater to stacks and normalize newline in JugglerSequence

* Fix: Normalize newline in JugglerSequence to ensure test consistency

* Fix: Normalize newline in JugglerSequence and remove return statement

* Add JaCoCo plugin for code coverage reporting

* Revert pom.xml to original version from master

* Fix: Revert the pom.xml file

---------

Co-authored-by: Deniz Altunkapan <deniz.altunkapan@outlook.com>

src/test/java/com/thealgorithms/stacks/TrappingRainwaterTest.java

@@ -0,0 +1,38 @@
+package com.thealgorithms.stacks;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class TrappingRainwaterTest {
+
+    @Test
+    public void testExampleCase() {
+        int[] height = {4, 2, 0, 3, 2, 5};
+        assertEquals(9, TrappingRainwater.trap(height));
+    }
+
+    @Test
+    public void testNoTrapping() {
+        int[] height = {1, 2, 3, 4, 5};
+        assertEquals(0, TrappingRainwater.trap(height));
+    }
+
+    @Test
+    public void testFlatSurface() {
+        int[] height = {0, 0, 0, 0};
+        assertEquals(0, TrappingRainwater.trap(height));
+    }
+
+    @Test
+    public void testSymmetricPit() {
+        int[] height = {3, 0, 2, 0, 3};
+        assertEquals(7, TrappingRainwater.trap(height));
+    }
+
+    @Test
+    public void testSingleBar() {
+        int[] height = {5};
+        assertEquals(0, TrappingRainwater.trap(height));
+    }
+}