Add math run and fraction

src/file/paragraph/math/fraction/math-numerator.ts

@@ -0,0 +1,11 @@
+import { XmlComponent } from "file/xml-components";
+
+import { MathRun } from "../math-run";
+
+export class MathNumerator extends XmlComponent {
+    constructor(readonly text: string) {
+        super("m:num");
+
+        this.root.push(new MathRun(text));
+    }
+}