i3bar: use Pango markup

Parse text within workspace buttons and the i3bar statusline as Pango
markup. This lets people specify things like font weight, text color,
background color, font size, and font family in the text of i3bar.

fixes #1468

docs/i3bar-protocol

@@ -119,7 +119,8 @@ click_events::
 full_text::
 	The most simple block you can think of is one which just includes the
 	only required key, the +full_text+ key. i3bar will display the string
-	value and that’s it.
+	value parsed as
+	https://developer.gnome.org/pango/stable/PangoMarkupFormat.html[Pango markup].
 short_text::
 	Where appropriate, the +short_text+ (string) entry should also be
 	provided. It will be used in case the status line needs to be shortened

docs/userguide

@@ -1625,6 +1625,10 @@ container to the next/previous workspace and +move container to workspace curren
 See <<move_to_outputs>> for how to move a container/workspace to a different
 RandR output.
 
+Workspace names are parsed as
+https://developer.gnome.org/pango/stable/PangoMarkupFormat.html[Pango markup]
+by i3bar.
+
 [[back_and_forth]]
 To switch back to the previously focused workspace, use +workspace
 back_and_forth+; likewise, you can move containers to the previously focused
@@ -1646,6 +1650,7 @@ move [window|container] [to] workspace <prev|next|current>
 -------------------------
 bindsym $mod+1 workspace 1
 bindsym $mod+2 workspace 2
+bindsym $mod+3 workspace 3:<span foreground="red">vim</span>
 ...
 
 bindsym $mod+Shift+1 move container to workspace 1