feat(plugins/leetcode): add plugin (#1213) [skip ci]

source/plugins/leetcode/queries/languages.graphql

@@ -0,0 +1,8 @@
+query Languages ($username: String!) {
+  matchedUser(username: $username) {
+    languageProblemCount {
+      languageName
+      problemsSolved
+    }
+  }
+}