Log Message:
editors: Add tepl4

Tepl is a library that eases the development of GtkSourceView-based text
editors and IDEs. Tepl is the acronym for "Text editor product line". It
serves as an incubator for GtkSourceView.

Tepl was previously named Gtef (GTK+ text editor framework). The project
has been renamed in June 2017 to have a more beautiful name. The end of Tepl
is pronounced like in "apple".