add initial marp implementation with sample content and build configuration

node_modules/@marp-team/marpit/lib/postcss/import/hoisting.js

@@ -0,0 +1,51 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.importHoisting = 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 import hoisting plugin.
+ *
+ * Hoist `@charset` and `@import` at-rule to the beginning of CSS. Marpit is
+ * manipulating CSS with many PostCSS plugins, so sometimes a few at-rules
+ * cannot keep specification.
+ *
+ * This plugin takes care of hoisting for invalid at-rules.
+ *
+ * @function importHoisting
+ */
+const importHoisting = exports.importHoisting = (0, _postcss_plugin.default)('marpit-postcss-import-hoisting', () => css => {
+  const hoisted = {
+    charset: undefined,
+    imports: []
+  };
+  css.walkAtRules(rule => {
+    if (rule.name === 'charset') {
+      rule.remove();
+      if (!hoisted.charset) hoisted.charset = rule;
+    } else if (rule.name === 'import') {
+      hoisted.imports.push(rule.remove());
+    }
+  });
+  const {
+    first
+  } = css
+
+  // Hoist at-rules
+  ;
+  [hoisted.charset, ...hoisted.imports].filter(r => r).forEach((rule, idx) => {
+    // Strip whitespace from the beginning of first at-rule
+    const prependRule = idx === 0 ? rule.clone({
+      raws: {
+        before: undefined
+      }
+    }) : rule;
+    first.before(prependRule);
+  });
+});
+var _default = exports.default = importHoisting;