add unit test

.woodpecker/test.yaml

@@ -0,0 +1,24 @@
+matrix:
+  platform:
+    - linux/amd64
+
+labels:
+  platform: ${platform}
+    
+steps:
+  test:
+    when:
+      event: [push]
+    image: alpine:latest
+    commands:
+      - apk update
+      - apk add --no-cache bash build-base gdb pkgconfig meson ninja perl ind-tools
+      - meson setup --reconfigure build
+      - ninja -C build
+      - build/udpxd -l 127.0.0.1:53 -t 8.8.8.8:53 &
+      - dig +nocmd +noall +answer google.de a @127.0.0.1
+      - killall udpxd
+      - udpxd -l [::1]:53 -t [2001:4860:4860::8888]:53 &
+      - dig +nocmd +noall +answer google.de a @::1
+      - killall udpxd
+