chore: update README

README.md

 # mquery (placeholder name)
 A Rust library for handling PROMQL (and possibly MetricsQL) queries.
 
+# Usage Example
+```rust
+use mquery::{Auth, QueryManager};
+use tokio::runtime::Runtime;
+
+dotenv::dotenv().expect("No .env file found in working dir");
+let url = std::env::var("VM_URL").expect("VM URL not found in env");
+let token = std::env::var("VM_TOKEN").expect("VM URL not found in env");
+let rt = Runtime::new().unwrap();
+let query = "total_http_requests";
+let _response = rt
+    .block_on(
+        QueryManager::new(url.parse().unwrap())
+            .auth(Auth::Bearer(token))
+            .query(query),
+    )
+    .expect("operation failed");
+}
+```
+
 # Roadmap
 - [x] Basic raw queries (Instant and Ranged)
 - [ ] Query Builder
   - [ ] Basic queries
   - [ ] Operators
   - [ ] Functions
+- [ ] Runtime syntax checking
 - [ ] Compile time syntax checking
-- [ ] Deserialize to custom data types
+- [ ] Deserialize to custom data types (with the help of proc-macros?)
 - [ ] Encapsulated raw queries with methods for constructing interpolated versions