Add findBase(name) method (#97)

Author: filip26

src/main/java/com/apicatalog/multibase/MultibaseDecoder.java

@@ -85,6 +85,26 @@ public Optional<Multibase> getBase(final String encoded) {
         return getBase(encoded.charAt(0));
     }
 
+    /**
+     * Finds a registered {@link Multibase} encoding by its name.
+     *
+     * <p>
+     * This method searches through all multibases registered with this decoder and
+     * returns the first whose {@link Multibase#name()} matches the given name
+     * exactly.
+     * </p>
+     *
+     * @param name the name of the multibase encoding (must not be {@code null})
+     * @return an {@code Optional} containing the matching {@link Multibase}, or an
+     *         empty {@code Optional} if no encoding with the given name is found
+     * @throws NullPointerException if {@code name} is {@code null}
+     */
+    public final Optional<Multibase> findBase(final String name) {
+        return bases.values().stream()
+                .filter(base -> base.name().equals(name))
+                .findFirst();
+    }
+
     /**
      * Decodes a multibase-encoded string into a byte array.
      *