Feature: #107081 - Add options to predefine link target and class in link browser 

Description 

The link browser now supports preconfiguring link target and class attributes. This allows administrators to set global defaults for all link types or specific defaults per handler type, reducing manual selection effort for editors.

Configuration can be set via Page TSconfig:

TCEMAIN.linkHandler.[handlerKey].(target|cssClass).default = _blank

Where handler keys correspond to the link handler types that support these attributes:

• page - for page links
• file - for file links
• folder - for folder links
• url - for external URLs
• telephone - for telephone links
• email - for email links

Global configuration (applies to all link types):

TCEMAIN.linkHandler.properties{
    target.default = _self
    cssClass.default = my-link-class
}

Handler-specific configuration (overrides global settings):

TCEMAIN.linkHandler{
    url.target.default = _blank
    page.target.default = _self
    file.cssClass.default = file-link
}

RTE.buttons.link{
    properties.target.default = _blank
    page.properties.target.default = _blank
}

Impact 

This feature improves editor workflows by providing meaningful default values for link attributes while preserving full flexibility for customization. The hierarchical configuration system allows both global defaults and handler-specific overrides, making link creation faster and more consistent.