ci: add rumdl

Author: chrisgrieser

.github/workflows/rumdl-lint.yml

@@ -0,0 +1,22 @@
+name: Markdown linting via rumdl
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - "**/*.md"
+      - ".github/workflows/rumdl-lint.yml"
+      - ".rumdl.toml"
+  pull_request:
+    paths:
+      - "**/*.md"
+
+jobs:
+  rumdl:
+    name: rumdl
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: rvben/rumdl@v0
+        with:
+          report-type: annotations

.rumdl.toml

@@ -0,0 +1,45 @@
+# DOCS https://github.com/rvben/rumdl/blob/main/docs/global-settings.md
+
+[global]
+line-length = 80
+disable = ["blanks-around-lists"]  # rule of proximity
+
+# ------------------------------------------------------------------------------
+
+[ul-style]
+style = "dash"  # GitHub default & quicker to type
+
+[ul-indent]
+indent = 4  # consistent with .editorconfig
+
+[line-length]
+code-blocks = false
+reflow = true  # enable auto-formatting
+
+[blanks-around-headings]
+lines-below = 0  # rule of proximity
+
+[ol-prefix]
+style = "ordered"
+
+[no-inline-html]
+allowed-elements = ["a", "img", "kbd"]  # badges
+
+[emphasis-style]
+style = "asterisk"  # better than underscore, since not considered a word-char
+
+[strong-style]
+style = "asterisk"
+
+[table-format]
+enabled = true  # opt-in rule
+
+[heading-capitalization]
+enabled = true  # opt-in rule
+style = "sentence_case"
+ignore-words = ["nvim", "Obsidian", "Alfred"]
+
+# ------------------------------------------------------------------------------
+
+[per-file-ignores]
+".github/pull_request_template.md" = ["first-line-h1"]