Fixed typos.

README.md

@@ -21,14 +21,14 @@ Here are some images:
 ## How to compile it
 
 * Download the [cc65 package](https://cc65.github.io/) which contains the C compiler, assembler and linker for the 6502 (NES).
-* In Windows:
+* On Windows:
   * You can execute the following command to compile the game (make sure you have **cc65-installation-path/bin** directory in your PATH environment. If not, you can edit the **compile.bat** file and change the directory **D:\Installations\cc65-snapshot-win32\bin\** for your directory):
 
 ```bash
 .\compile.bat
 ```
 
-* In Linux:
+* On Linux:
   * You can execute the following command to compile the game (make sure the **bin** directory of **cc65** is in your **PATH** env):
 
 ```bash