Add Wikipedia reference to LinearEquation

Author: arthurfellipe-dev

src/main/java/com/thealgorithms/maths/LinearEquation.java

@@ -3,6 +3,12 @@
 /**
  * Solves linear equations of the form ax + b = 0.
  */
+
+/**
+ * Solves linear equations of the form ax + b = 0.
+ *
+ * @see <a href="https://en.wikipedia.org/wiki/Linear_equation">Linear equation (Wikipedia)</a>
+ */
 public final class LinearEquation {
 
     private LinearEquation() {