Add option to use user mailcap

Added the option to have a `mailcap` file in `.config/mutt/`. This enables ease of changing what programs are used for viewing.

share/mutt-wizard.muttrc

@@ -3,7 +3,7 @@
 # mutt-wizard will have this file sourced from your muttrc.
 # In the interest of seamless updating, do not edit this file.
 # If you want to override any settings, set those in your muttrc.
-set mailcap_path = /usr/local/share/mutt-wizard/mailcap:$mailcap_path
+set mailcap_path = $HOME/.config/mutt/mailcap:/usr/local/share/mutt-wizard/mailcap:$mailcap_path
 set mime_type_query_command = "file --mime-type -b %s"
 set date_format="%y/%m/%d %I:%M%p"
 set index_format="%2C %Z %?X?A& ? %D %-15.15F %s (%-4.4c)"