fix(dsl): support serializing Double (#1485)

Author: haifengkao

github-workflows-kt/src/main/kotlin/io/github/typesafegithub/workflows/yaml/ObjectToYaml.kt

@@ -45,7 +45,7 @@ private fun Any?.elementToYaml(emitter: Emitter) {
     when (this) {
         is Map<*, *> -> this.mapToYaml(emitter)
         is List<*> -> this.listToYaml(emitter)
-        is String, is Int, is Float, is Boolean, null -> this.scalarToYaml(emitter)
+        is String, is Int, is Float, is Double, is Boolean, null -> this.scalarToYaml(emitter)
         else -> error("Serializing $this is not supported!")
     }
 }

github-workflows-kt/src/test/kotlin/io/github/typesafegithub/workflows/yaml/ObjectToYamlTest.kt

@@ -33,6 +33,7 @@ class ObjectToYamlTest : DescribeSpec({
                         "bar",
                         123,
                         456.789f,
+                        11.22,
                         listOf(
                             mapOf("another-foo" to 123),
                             mapOf("key-with-null-value" to null),
@@ -54,6 +55,7 @@ class ObjectToYamlTest : DescribeSpec({
             - 'bar'
             - 123
             - 456.789
+            - 11.22
             - - another-foo: 123
               - key-with-null-value: null
               - key-with-null-map: {}