Add Javadoc comments for AnyBaseToAnyBase class (#7301)

Added Javadoc comments to describe the algorithm and its complexities.

src/main/java/com/thealgorithms/conversions/AnyBaseToAnyBase.java

@@ -1,3 +1,10 @@
+/**
+ * [Brief description of what the algorithm does]
+ * <p>
+ * Time Complexity: O(n) [or appropriate complexity]
+ * Space Complexity: O(n)
+ * * @author Reshma Kakkirala
+ */
 package com.thealgorithms.conversions;
 
 import java.util.Arrays;