added some code dependencies and maintenance

entries/gtk.md

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+# GTK
+
+_Multi-platform toolkit for creating graphical user interfaces._
+
+- Home: https://www.gtk.org/
+- State: mature
+- Download: https://www.gtk.org/download/index.php
+- Platform: Windows, Linux, macOS
+- Keywords: library
+- Code repository: https://gitlab.gnome.org/GNOME/gtk.git
+- Code language: C
+- Code license: LGPL-2.1
+
+## Building
+
+- Build system: meson