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

Description 

The LinkBrowser 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 link handlers that support these attributes:

- page (for page links)
- file (for file links)
- folder (for folder links)
- url (for external URL links)
- telephone (for telephone number css class)
- email (for email css class)

Global configuration (applies to all link types):

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

Handler-specific configuration (overrides global settings):

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

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

For details, see buttons.link.[ type ].properties.target.default.

Impact 

This feature improves editor workflow by providing sensible defaults for link attributes while maintaining full flexibility to override when needed. The hierarchical configuration allows both global policies and specific handler customization.