Turn Run into a declaritive API

src/file/paragraph/run/text-run.ts

@@ -1,9 +1,19 @@
-import { Run } from "../run";
+import { IRunOptions, Run } from "./run";
 import { Text } from "./run-components/text";
 
+export interface ITextRunOptions extends IRunOptions {
+    readonly text: string;
+}
+
 export class TextRun extends Run {
-    constructor(text: string) {
-        super();
-        this.root.push(new Text(text));
+    constructor(options: ITextRunOptions | string) {
+        if (typeof options === "string") {
+            super({});
+            this.root.push(new Text(options));
+            return;
+        }
+
+        super(options);
+        this.root.push(new Text(options.text));
     }
 }