Emphasize lines with things to replace in autostart guides (#5548)

* Emphasize lines with things to replace in autostart guides

* Use 'default' pygments style instead

docs/autostart_mac.rst

@@ -20,11 +20,12 @@ Now run :code:`sudo nano /Library/LaunchDaemons/red.plist`
 
 Paste the following and replace the following: 
 
-- all instances of :code:`username` with your Mac username 
+- :code:`username` (but not :code:`UserName`) with your Mac username
 - :code:`path` with the path you copied earlier
 - :code:`instance-name` with your instance name:
 
 .. code-block:: none
+    :emphasize-lines: 9, 13, 28
 
     <?xml version="1.0" encoding="UTF-8"?>
     <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">

docs/autostart_systemd.rst

@@ -39,6 +39,7 @@ Then create the new service file:
 Paste the following in the file, and replace all instances of :code:`username` with the Linux username you retrieved above, and :code:`path` with the python path you retrieved above.
 
 .. code-block:: none
+    :emphasize-lines: 8-10
 
     [Unit]
     Description=%I redbot

docs/conf.py

@@ -96,7 +96,7 @@ exclude_patterns = [
 ]
 
 # The name of the Pygments (syntax highlighting) style to use.
-pygments_style = "sphinx"
+pygments_style = "default"
 
 # If true, `todo` and `todoList` produce output, else they produce nothing.
 todo_include_todos = False