fix: configure markdownlint-cli2 properly

- Wrap config in 'config' key for markdownlint-cli2
- Use MD013 rule name instead of 'line-length' alias
- Disable MD013 line-length checks
- Add allowed languages: sh, python, csv, tree
- Fix broken link reference in TODO.md
- All markdown linting now passes (37 errors -> 0)

.prettierrc.json

@@ -0,0 +1,40 @@
+{
+  "$schema": "https://json.schemastore.org/prettierrc.json",
+  "arrowParens": "always",
+  "bracketSpacing": true,
+  "embeddedLanguageFormatting": "auto",
+  "htmlWhitespaceSensitivity": "css",
+  "insertPragma": false,
+  "jsxSingleQuote": false,
+  "printWidth": 100,
+  "proseWrap": "preserve",
+  "quoteProps": "as-needed",
+  "requirePragma": false,
+  "semi": true,
+  "singleQuote": false,
+  "useTabs": false,
+  "overrides": [
+    {
+      "files": ["*.html"],
+      "options": {
+        "parser": "jinja-template"
+      }
+    },
+    {
+      "files": ["*.md", "*.markdown"],
+      "options": {
+        "tabWidth": 2,
+        "useTabs": false,
+        "proseWrap": "preserve",
+        "printWidth": 100
+      }
+    },
+    {
+      "files": ["*.jsonc"],
+      "options": {
+        "trailingComma": "none"
+      }
+    }
+  ],
+  "plugins": ["prettier-plugin-jinja-template", "prettier-plugin-packagejson"]
+}