ci: add markdown linter and fix all linting errors

Signed-off-by: Nathan Weinberg <[email protected]>

.github/workflows/docs.yml

@@ -0,0 +1,23 @@
+name: docs
+
+on:
+  push:
+    branches: ["main"]
+    paths:
+      - '**/*.md'
+      - '.markdownlint-cli2.yaml'
+  pull_request:
+    branches: ["main"]
+    paths:
+      - '**/*.md'
+      - '.markdownlint-cli2.yaml'
+
+jobs:
+  markdown-lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: markdownlint-cli2-action
+        uses: DavidAnson/markdownlint-cli2-action@v15
+        with:
+          globs: '**/*.md'

.markdownlint-cli2.yaml

@@ -0,0 +1,13 @@
+config:
+  line-length: false
+  no-emphasis-as-header: false
+  first-line-heading: false
+  code-block-style: false
+  no-duplicate-header: false
+  single-trailing-newline: false
+globs:
+  - "**/*.md"
+ignores:
+  - ".tox/**"
+  - "venv/**"
+  - ".venv/**"

Makefile

@@ -0,0 +1,22 @@
+.PHONY: help
+help:
+	@awk 'BEGIN {FS = ":.*##"; printf "\nUsage:\n  make \033[36m<target>\033[0m\n"} /^[a-zA-Z_0-9-]+:.*?##/ { printf "  \033[36m%-18s\033[0m %s\n", $$1, $$2 } /^##@/ { printf "\n\033[1m%s\033[0m\n", substr($$0, 5) } ' $(MAKEFILE_LIST)
+
+#
+# If you want to see the full commands, run:
+#   NOISY_BUILD=y make
+#
+ifeq ($(NOISY_BUILD),)
+    ECHO_PREFIX=@
+    CMD_PREFIX=@
+    PIPE_DEV_NULL=> /dev/null 2> /dev/null
+else
+    ECHO_PREFIX=@\#
+    CMD_PREFIX=
+    PIPE_DEV_NULL=
+endif
+
+.PHONY: md-lint
+md-lint: ## Lint markdown files
+	$(ECHO_PREFIX) printf "  %-12s ./...\n" "[MD LINT]"
+	$(CMD_PREFIX) podman run --rm -v $(CURDIR):/workdir --security-opt label=disable docker.io/davidanson/markdownlint-cli2:v0.12.1 > /dev/null