feat(Kotlin): Replace value with _val (#1254)

* ci(kotlin): Add workflow file.

* Update kotlin.yml

* style(kotlin): value -> _val

---------

Co-authored-by: Yudong Jin <krahets@163.com>

codes/kotlin/utils/Vertex.kt

@@ -7,7 +7,7 @@
 package utils
 
 /* 顶点类 */
-class Vertex(val value: Int) {
+class Vertex(val _val: Int) {
     companion object {
         /* 输入值列表 vals ，返回顶点列表 vets */
         fun valsToVets(vals: IntArray): Array<Vertex?> {
@@ -22,7 +22,7 @@ class Vertex(val value: Int) {
         fun vetsToVals(vets: MutableList<Vertex?>): MutableList<Int> {
             val vals = mutableListOf<Int>()
             for (vet in vets) {
-                vals.add(vet!!.value)
+                vals.add(vet!!._val)
             }
             return vals
         }