Improve the plotting text tutorial. Add a link to the matching doc

On add a link to

Appropriate text might be: Further details, including using special symbols and other character sets can be found at

After a lot of searching, that is where I found out to use @. to enter a degree symbol in text on a map.

Thanks for the suggestion! If you want, you could take a look at to see if it is more clear now with a preview at

They look great. Thank you.