feat(kotlin): add draft field to Pull request

Author: Vacxe

danger-kotlin-library/src/main/kotlin/systems/danger/kotlin/models/github/GitHub.kt

@@ -76,6 +76,7 @@ data class GitHubPR(
     val head: GitHubMergeRef,
     val base: GitHubMergeRef,
     val state: GitHubPullRequestState,
+    val draft: Boolean,
     @SerialName("locked") val isLocked: Boolean,
     @SerialName("merged") val isMerged: Boolean?,
     @SerialName("commits") val commitCount: Int?,

danger-kotlin-library/src/test/resources/githubDangerJSON.json

@@ -512,6 +512,7 @@
           "issue_url": "https://api.github.com/repos/artsy/eidolon/issues/609",
           "number": 609,
           "state": "closed",
+          "draft": false,
           "locked": false,
           "title": "Xcode updates",
           "user": {

danger-kotlin-library/src/test/resources/githubWithClosedMilestoneDangerJSON.json

@@ -512,6 +512,7 @@
           "issue_url": "https://api.github.com/repos/artsy/eidolon/issues/609",
           "number": 609,
           "state": "closed",
+          "draft": false
           "locked": false,
           "title": "Xcode updates",
           "user": {

danger-kotlin-library/src/test/resources/githubWithSomeNullsAttributeDangerJSON.json

@@ -512,6 +512,7 @@
           "issue_url": "https://api.github.com/repos/artsy/eidolon/issues/609",
           "number": 609,
           "state": "closed",
+          "draft": false,
           "locked": false,
           "title": "Xcode updates",
           "user": {