Add abstruse ci config

.abstruse.yml

@@ -0,0 +1,13 @@
+image: openjdk:8-jdk
+
+matrix:
+  - env: SCRIPT=shadowJar
+
+before_install:
+  - apt update
+
+install:
+  - apt install -y gradle
+
+script:
+  - if [[ "SCRIPT" ]]; then gradle $SCRIPT; fi