doc: Add bacj an accidently removed section. (#2885)

This was probably due to copy pasting from the preprocessed file
back to the raw file.

Fix #2882

awesomerc.lua

@@ -22,6 +22,7 @@ require("awful.hotkeys_popup.keys")
 -- {{{ Error handling
 -- Check if awesome encountered an error during startup and fell back to
 -- another config (This code will only ever execute for the fallback config)
+-- @DOC_ERROR_HANDLING@
 naughty.connect_signal("request::display_error", function(message, startup)
     naughty.notification {
         urgency = "critical",

docs/05-awesomerc.md.lua

@@ -29,6 +29,7 @@ Here are the modules that we import:
 ]]
 
 sections.DOC_ERROR_HANDLING = [[
+
 Awesome is a window managing framework. It allows its users great (ultimate?)
 flexibility. However, it also allows the user to write invalid code. Here's a
 non-exhaustive list of possible errors: