added stdPr and stdContent to table of contents

src/file/table-of-contents/std-content.ts

@@ -0,0 +1,12 @@
+import { Paragraph } from "file/paragraph";
+import { XmlComponent } from "file/xml-components";
+
+export class StdContent extends XmlComponent {
+    constructor() {
+        super("w:stdContent");
+    }
+
+    public addGeneratedContent(paragraph: Paragraph): void {
+        this.root.splice(this.root.length - 1, 0, paragraph);
+    }
+}