Update README.md

added  destroy function to thread examples

Author: Psychloor

README.md

@@ -37,11 +37,13 @@ This library implements the widely accepted solution: running physics at a fixed
 void* physics_thread(void* arg) {
     TimeManager* tm = TmCreate(NULL);
     // ... use tm only in this thread
+    TmDestroy(tm);
 }
 
 void* ai_thread(void* arg) {
     TimeManager* tm = TmCreate(NULL);
     // ... use tm only in this thread
+    TmDestroy(tm);
 }
 
 // Also good: Single-threaded game loop
@@ -52,6 +54,7 @@ int main() {
         FrameTimingData frame = TmBeginFrame(tm);
         // All timing happens on main thread
     }
+    TmDestroy(tm);
 }
 ```
 ## Building
@@ -276,4 +279,4 @@ Licensed under the MIT License. See LICENSE for more information.
 
 ## Contributing
 
-Contributions are welcome! Please feel free to submit pull requests or open issues for bugs and feature requests.
+Contributions are welcome! Please feel free to submit pull requests or open issues for bugs and feature requests.