The text on the welcome page should be customizable.
This request stems from the need to provide information on organization-specific rules and link to an intranet page.

A new registry key must be defined to store user-specific text.
The key can have a language-specific suffix.

If such a key is defined, only the first two lines of the existing text on the welcome screen will be kept.

Welcome to Kleopatra 4.0.0.250801
Kleopatra is a front-end for the crypto software GnuPG.

The following text is replaced by (a separation line and) the content of the defined registry key.

Technically, we'll use a config key for this. Config keys support localized values out-of-the-box (see the filter names). On Windows, the config keys can be set in the registry.