Add new Discussions plugin (#430) [skip ci]

source/plugins/discussions/queries/categories.graphql

@@ -0,0 +1,15 @@
+query DiscussionsCategories {
+  user(login: "$login") {
+    repositoryDiscussions($after first: 100, orderBy: {field: CREATED_AT, direction: DESC}) {
+      edges {
+        cursor
+      }
+      nodes {
+        category {
+          emoji
+          name
+        }
+      }
+    }
+  }
+}

source/plugins/discussions/queries/statistics.graphql

@@ -0,0 +1,13 @@
+query DiscussionsStatistics {
+  user(login: "$login") {
+    started: repositoryDiscussions {
+      totalCount
+    }
+    comments: repositoryDiscussionComments {
+      totalCount
+    }
+    answers: repositoryDiscussionComments(onlyAnswers: true) {
+      totalCount
+    }
+  }
+}