ci: Add a basic ci config

Do things like build docs, check fmt, clippy and build in non-release
and release mode as well as the debian package. Include a badge which
reflects the status of the ci for the main branch to the readme.

.woodpecker.yml

@@ -0,0 +1,29 @@
+pipeline:
+  doc:
+    image: rust
+    commands:
+      - cargo doc
+
+  fmt:
+    image: rust
+    commands:
+      - rustup component add rustfmt
+      - cargo fmt --all -- --check
+
+  clippy:
+    image: rust
+    commands:
+      - rustup component add clippy
+      - cargo clippy --all-features
+
+  build:
+    image: rust
+    commands:
+      - cargo build
+      - cargo build --release
+
+  build-deb:
+    image: rust
+    commands:
+      - cargo install cargo-deb
+      - cargo deb

README.md

@@ -1,4 +1,6 @@
 # Webhookey
+![status-badge](https://ci.onders.org/api/badges/finga/webhookey/status.svg?branch=main)
+
 Webhookey is a web server listening for
 [webhooks](https://en.wikipedia.org/wiki/Webhook) as for example sent
 by Gitea's webhooks. Further, Webhookey allows you to specify rules