Rewording of README information for learnr

[sof202]

The readme currently reads:

If the tutorial doe snot automatically launch in a new windonw, to launch it copy the web address in this case (http://127.0.0.1:38555/) into a web browser of your choice, such as Chrome.

However, as stated, this is not guaranteed to be correct. I think it might be more clear if the readme highlights the part of the screenshot (already given) that gives the actual web address the course notes are being hosted on.

Giving a hyperlink to those who are already convinced the learnr command didn't work might be misleading if the port number given is incorrect (as the hyperlink will therefore also not work and most will just blindly click on it).

Hopefully this makes sense.

There's also a couple of spelling mistakes on this line I guess, but this is less important.