Create Atoi Function.java (#3756)

* Create MyAtoi.java

There is a method in C++, which converts String to an Integer, called Atoi function, this is my own implementation of this function.

* Update directory

* Update MyAtoi.java

* Create MyAtoiTest.java

* Update directory

* Update directory

* Update directory

* Update MyAtoi.java

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: Debasish Biswas <debasishbsws.abc@gmail.com>

src/test/java/com/thealgorithms/strings/MyAtoiTest.java

@@ -0,0 +1,25 @@
+package com.thealgorithms.strings;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class MyAtoiTest {
+	
+    @Test
+    void testOne() {
+        assertEquals(42, MyAtoi.myAtoi("42"));
+    }
+  
+      @Test
+    void testTwo() {
+        assertEquals(-42, MyAtoi.myAtoi("   -42"));
+    }
+  
+  
+      @Test
+    void testThree() {
+        assertEquals(4193, MyAtoi.myAtoi("4193 with words"));
+    }
+	
+}