Added support for w:fldSimple, including convenience class for simple MailMerge fields

src/file/paragraph/run/simple-field.ts

@@ -0,0 +1,23 @@
+// http://www.datypic.com/sc/ooxml/e-w_fldSimple-1.html
+import { XmlAttributeComponent, XmlComponent } from "file/xml-components";
+import { TextRun } from "./text-run";
+
+class FldSimpleAttrs extends XmlAttributeComponent<{ readonly instr: string }> {
+    protected readonly xmlKeys = { instr: "w:instr" };
+}
+
+export class SimpleField extends XmlComponent {
+    constructor(instruction: string, cachedValue?: string) {
+        super("w:fldSimple");
+        this.root.push(new FldSimpleAttrs({ instr: instruction }));
+        if (cachedValue !== undefined) {
+            this.root.push(new TextRun(cachedValue));
+        }
+    }
+}
+
+export class SimpleMailMergeField extends SimpleField {
+    constructor(fieldName: string) {
+        super(` MERGEFIELD ${fieldName} `, `«${fieldName}»`);
+    }
+}