ci: run everything in pipeline in parallel

.woodpecker.yml

@@ -1,34 +1,40 @@
 pipeline:
-  doc:
-    image: rust
-    commands:
-      - cargo doc
-
   fmt:
+    group: default
     image: rust
     commands:
       - rustup component add rustfmt
       - cargo fmt --all -- --check
 
   clippy:
+    group: default
     image: rust
     commands:
       - rustup component add clippy
       - cargo clippy --all-features
 
   test:
+    group: default
     image: rust
     commands:
       - cargo test
 
   build:
+    group: default
     image: rust
     commands:
       - cargo build
       - cargo build --release
 
   build-deb:
+    group: default
     image: rust
     commands:
       - cargo install cargo-deb
       - cargo deb
+
+  doc:
+    group: default
+    image: rust
+    commands:
+      - cargo doc