add mutations for comments

src/operations/comments.gql

@@ -0,0 +1,19 @@
+mutation CommentOnVideo(
+  $videoId: Int!
+  $message: String!
+  $parentCommentId: Int
+) {
+  commentOnVideo(
+    videoId: $videoId
+    message: $message
+    parentCommentId: $parentCommentId
+  )
+}
+
+mutation EditComment($videoId: Int!, $commentId: Int!, $newMessage: String!) {
+  editComment(videoId: $videoId, commentId: $commentId, newMessage: $newMessage)
+}
+
+mutation DeleteComment($videoId: Int!, $commentId: Int!) {
+  deleteComment(videoId: $videoId, commentId: $commentId)
+}