added append function

src/main/java/strman/Strman.java

@@ -1,9 +1,31 @@
 package strman;
 
+import java.util.StringJoiner;
+
 /**
  * A String manipulation library without any dependencies
  */
 public interface Strman {
 
 
+    /**
+     * Appends Strings to value
+     *
+     * @param value   initial String
+     * @param appends -- an array of strings to append
+     * @return full string
+     */
+    static String append(final String value, final String... appends) throws IllegalArgumentException {
+        if (value == null) {
+            throw new IllegalArgumentException("'value' should be not null.");
+        }
+        if (appends == null || appends.length == 0) {
+            return value;
+        }
+        StringJoiner joiner = new StringJoiner("");
+        for (String append : appends) {
+            joiner.add(append);
+        }
+        return value + joiner.toString();
+    }
 }