Fixes `sh: 1: cannot create /home/<username>/.cache/mutt_terms:
Directory nonexistent`.

According to:
  https://neomutt.org/guide/reference.html#3-380-%C2%A0realname
  https://neomutt.org/guide/reference.html#3-480-%C2%A0spoolfile

`+` was properly escaped but only once. `$` was not escaped at all.
This would result in messages with message IDs containing more than one
`+` or at least on `$` to not be shown after limiting.
`$` itself has to be escaped presumably for the shell. This results in
three prepended backslashes in the limit string and six in the config
file, as there backslashes themselves have to be escaped.

added fidei.email service provider

This reverts commit 67b704808d.

For increased legibility.

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

avoid line splitting.
the width option is set to 80 by default, increasing it will avoid breaking long links in two different lines