Update 'README.md'

README.md

@@ -3,10 +3,10 @@ Project is provided with already built ORB_SLAM3.lib library. You might want to
 
 ## If you downloaded ORB_SLAM3 from the official repository, all you need to do is: 
 1. Add unistd.h and getopt.c and getopt.h to include/ folder. 
-2. Add `void usleep(__int64 usec);` to `Sytem.h` before `namespace ORB_SLAM3`, and add: 
-void usleep(__int64 usec){
-    std::this_thread::sleep_for(std::chrono::microseconds(usec));
-}
+2. Add `void usleep(__int64 usec);` to `Sytem.h` before `namespace ORB_SLAM3`, and add:  
+void usleep(__int64 usec){  
+    std::this_thread::sleep_for(std::chrono::microseconds(usec));  
+}  
 to the `System.cc`file before `namespace ORB_SLAM3`. 
 
 ## Prerequisites