Add .gitlab-ci.yml

.gitlab-ci.yml

+image: fedora:latest
+stages:
+  - build
+
+build:
+  stage: build
+  script:
+  - dnf install -y 'pkgconfig(gtk+-3.0)' gcc meson ninja-build
+  - meson builddir
+  - ninja -C builddir
\ No newline at end of file