Merge pull request #8030 from mikeshatch/patch-3

Corrected a typo and two grammar errors.

doc/00-intro.md

@@ -47,7 +47,7 @@ Linux and macOS.
 ### Downloading the Composer Executable
 
 Composer offers a convenient installer that you can execute directly from the
-commandline. Feel free to [download this file](https://getcomposer.org/installer)
+command line. Feel free to [download this file](https://getcomposer.org/installer)
 or review it on [GitHub](https://github.com/composer/getcomposer.org/blob/master/web/installer)
 if you wish to know more about the inner workings of the installer. The source
 is plain PHP.
@@ -82,7 +82,7 @@ Now run `php bin/composer` in order to run Composer.
 #### Globally
 
 You can place the Composer PHAR anywhere you wish. If you put it in a directory
-that is part of your `PATH`, you can access it globally. On unixy systems you
+that is part of your `PATH`, you can access it globally. On Unix systems you
 can even make it executable and invoke it without directly using the `php`
 interpreter.