Add CI job to run codespell on all source files

Fixes https://codeberg.org/openpgp/notes/issues/96

Signed-off-by: David Runge <dave@sleepmap.de>

.woodpecker/codespell.yml

@@ -0,0 +1,22 @@
+# SPDX-FileCopyrightText: 2023 The "Notes on OpenPGP" project
+# SPDX-License-Identifier: CC0-1.0
+
+clone:
+  git:
+    image: woodpeckerci/plugin-git
+    settings:
+      lfs: false
+
+when:
+  branch: draft
+  event:
+    - push
+    - pull_request
+
+steps:
+  codespell:
+    image: archlinux:latest
+    commands:
+      - pacman -Sy --needed --noconfirm archlinux-keyring
+      - pacman -Syu --needed --noconfirm codespell make
+      - make -C book codespell