add initial marp implementation with sample content and build configuration

node_modules/@marp-team/marpit/lib/postcss/root/replace.js

@@ -0,0 +1,26 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.rootReplace = exports.default = void 0;
+var _postcss_plugin = _interopRequireDefault(require("../../helpers/postcss_plugin"));
+function _interopRequireDefault(e) { return e && e.__esModule ? e : { default: e }; }
+/** @module */
+
+/**
+ * Marpit PostCSS root replace plugin.
+ *
+ * Replace `:root` pseudo-class selector into `section`. It can add custom
+ * pseudo class through `pseudoClass` option to make distinguishable from
+ * `section` selector.
+ *
+ * @function rootReplace
+ */
+const rootReplace = exports.rootReplace = (0, _postcss_plugin.default)('marpit-postcss-root-replace', ({
+  pseudoClass
+} = {}) => css => css.walkRules(rule => {
+  // Replace `:root` pseudo-class selectors into `section`
+  rule.selectors = rule.selectors.map(selector => selector.replace(/(^|[\s>+~(])(?:section)?:root\b/g, (_, s) => `${s}section${pseudoClass || ''}`));
+}));
+var _default = exports.default = rootReplace;