Schleuder: subscribers: make Cc examples more specific

See merge request !113

Before, some examples would only list one email address, while in fact,
these examples talk about multiple email addresses.

Ref !112

Add news about Schleuder 4.0.3

See merge request !112

List schleuder providers

Closes #12

See merge request !111

add documentation about archlinux packages

See merge request !110

Fix typos: encyrption is called encryption

See merge request !109

Add docs about Schleuder 4.0.1

See merge request !108

Make x-list-name bold, similar to all the other keywords

See merge request !106

subscribers: fix typo

See merge request !107

No master, but main, once more

See merge request !105

No master, but main

See merge request !104

Add bold font face

Closes #57

See merge request !103

Schleuder subscribers: Improve wording of 'key update' docs

See merge request !102

* Make the whole note about which key to sign with during the process
bold.

* Improve wording and make it more consistent.

* Fix typo.

improve description of command x-add-key

See merge request !101

if keys are send as attachment, they can also be in binary format

Make gitlab ci use main as main branch.

See merge request !100

add x-add-key command, add example how to update your key to subscribers docu

See merge request !98

fixes some spelling issues
uses real h5 headers, also listed in the TOC
adds spacing between the sections for better legibility

  adding &nbsp is a hack, but I did not want to start
  messing with the css

Schleuder 4.0.0

See merge request !96