fix 2^n check

src/commonMain/kotlin/com/infendro/encoding/stream/StreamEncoding.kt

@@ -11,7 +11,7 @@ open class StreamEncoding(
     private val padding: Byte? = null,
 ) : Encoding(alphabet) {
     init {
-        require(base % 2 == 0)
+        require(base and (base - 1) == 0)
     }
 
     override fun encode(bytes: ByteArray): ByteArray {