Add '.swp' as temp Vim extension in example

Although Vim uses files that end with '~', usually 'git status'
shows '.*.swp' file that is present during editing a file (~ file
is present only at saving time)

Author: hedrok

book/08-customizing-git/sections/config.asc

@@ -145,14 +145,15 @@ You can put patterns in your project's `.gitignore` file to have Git not see the
 
 But sometimes you want to ignore certain files for all repositories that you work with.
 If your computer is running Mac OS X, you're probably familiar with `.DS_Store` files.
-If your preferred editor is Emacs or Vim, you know about files that end with a `~`.
+If your preferred editor is Emacs or Vim, you know about files that end with a `~` or `.swp`.
 
 This setting lets you write a kind of global `.gitignore` file.
 If you create a `~/.gitignore_global` file with these contents:
 
 [source,ini]
 ----
 *~
+.*.swp
 .DS_Store
 ----