attribute builder now may skip nullable values

src/jsMain/kotlin/dev/inmo/jsuikit/UIKitAttributeValueBuilder.kt

@@ -24,9 +24,10 @@ class UIKitAttributeValueBuilder {
 
 fun AttrsBuilder<*>.buildAndAddAttribute(
     attributeName: String,
+    skipNullValues: Boolean = true,
     block: AttributeBuilder.() -> Unit
 ) {
-    buildAttribute(attributeName, block).let {
+    buildAttribute(attributeName, skipNullValues, block).let {
         attr(it.first, it.second)
     }
 }

src/jsMain/kotlin/dev/inmo/jsuikit/utils/AttributeBuilder.kt

@@ -2,10 +2,15 @@ package dev.inmo.jsuikit.utils
 
 class AttributeBuilder (
     val attributeName: String,
+    val skipNullValues: Boolean = true,
     private val parametersPreset: MutableMap<String, String?> = mutableMapOf()
 ) {
 
-    fun add(k: String, v: Any? = null) = parametersPreset.set(k, v ?.toString())
+    fun add(k: String, v: Any? = null) {
+        if (v != null || !skipNullValues) {
+            parametersPreset[k] = v ?.toString()
+        }
+    }
     infix fun String.to(value: Any?) = add(this, value)
     operator fun String.unaryPlus() = add(this, null)
 
@@ -16,6 +21,7 @@ class AttributeBuilder (
     )
 }
 
-inline fun buildAttribute(attributeName: String, block: AttributeBuilder.() -> Unit) = AttributeBuilder(
-    attributeName
+inline fun buildAttribute(attributeName: String, skipNullValues: Boolean = true, block: AttributeBuilder.() -> Unit) = AttributeBuilder(
+    attributeName,
+    skipNullValues
 ).apply(block).build()