Add examples/graphql_issues.rs

I could not find any examples of a real graphql query, so here comes
one. It would have helped me, so hopefully it will also help others.

examples/graphql_issues.rs

@@ -0,0 +1,28 @@
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
+    let octocrab = octocrab::Octocrab::builder()
+        .personal_token(std::env::var("GITHUB_TOKEN").unwrap())
+        .build()?;
+
+    let query = r#" {
+        repository(owner:"XAMPPRocky", name:"octocrab") {
+            issues(last: 2, states: OPEN) {
+                nodes {
+                    title
+                    url
+                }
+            }
+        }
+    } "#;
+
+    let response: octocrab::Result<serde_json::Value> = octocrab
+        .graphql(&serde_json::json!({ "query": query }))
+        .await;
+
+    match response {
+        Ok(value) => println!("{value:#?}"),
+        Err(error) => println!("{error:#?}"),
+    }
+
+    Ok(())
+}