ci: woodpecker: add exec pipeline

.woodpecker/docker.yml

@@ -0,0 +1,6 @@
+labels:
+  type: docker
+
+pipeline:
+  test:
+    image: hello-world

.woodpecker/exec.yml

@@ -0,0 +1,26 @@
+labels:
+  type: exec
+
+pipeline:
+  test:
+    image: bash
+    commands:
+    - "nix run 'nixpkgs#hello'"
+
+  notify:
+    image: bash
+    secrets:
+    - source: matrix_homeserver
+      target: address
+    - source: matrix_roomid
+      target: room
+    - source: matrix_username
+      target: user
+    - source: matrix_password
+      target: pass
+    commands:
+    - nix run 'github:ambroisie/matrix-notifier'
+    when:
+      status:
+      - failure
+      - success