Allow custom text properties to be included

src/file/custom-properties/custom-properties.ts

@@ -0,0 +1,41 @@
+import { IXmlableObject, XmlComponent } from "file/xml-components";
+import { CustomPropertiesAttributes } from "./custom-properties-attributes";
+import { CustomProperty, ICustomPropertyOptions } from "./custom-property";
+
+export class CustomProperties extends XmlComponent {
+    // tslint:disable-next-line:readonly-keyword
+    private nextId: number;
+    private readonly properties: CustomProperty[] = [];
+
+    constructor(properties: ICustomPropertyOptions[]) {
+        super("Properties");
+
+        this.root.push(
+            new CustomPropertiesAttributes({
+                xmlns: "http://schemas.openxmlformats.org/officeDocument/2006/custom-properties",
+                vt: "http://schemas.openxmlformats.org/officeDocument/2006/docPropsVTypes",
+            }),
+        );
+
+        // I'm not sure why, but every example I have seen starts with 2
+        // https://docs.microsoft.com/en-us/office/open-xml/how-to-set-a-custom-property-in-a-word-processing-document
+        this.nextId = 2;
+
+        for (const property of properties) {
+            this.addCustomProperty(property);
+        }
+    }
+
+    public prepForXml(): IXmlableObject | undefined {
+        this.properties.forEach((x) => this.root.push(x));
+        return super.prepForXml();
+    }
+
+    public addCustomProperty(property: ICustomPropertyOptions): void {
+        this.properties.push(new CustomProperty(this.nextId++, property));
+    }
+
+    public get Properties(): CustomProperty[] {
+        return this.properties;
+    }
+}