bug(email_widget): Fix widgets not accessible

When fixing linter warnings in
ed2b256407
the previously global values were made local but no return statement to
export them was added.

Signed-off-by: Lucas Schwiderski <lucas@lschwiderski.de>

email-widget/README.md

@@ -14,7 +14,8 @@ To install it put **email.lua** and **email-widget** folder under **~/.config/aw
  - add widget to awesome:
 
 ```lua
-require("email")
+local email_widget, email_icon = require("email")
+
 ...
 s.mytasklist, -- Middle widget
 	{ -- Right widgets

email-widget/email.lua

@@ -40,3 +40,5 @@ local function show_emails()
 end
 
 email_icon:connect_signal("mouse::enter", function() show_emails() end)
+
+return email_widget, email_icon