chore: addon generator to async/await (#849)

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**What kind of change does this PR introduce?**
refactor
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**Did you add tests for your changes?**
yes

**If relevant, did you update the documentation?**
NA

**Summary**
* Move async gen to async await.

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**Does this PR introduce a breaking change?**
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No

**Other information**
Not yet

packages/generators/addon-generator.ts

@@ -39,12 +39,9 @@ export default function addonGenerator(
 		public copy: (value: string, index: number, array: string[]) => void;
 		public copyTpl: (value: string, index: number, array: string[]) => void;
 
-		public prompting(): Promise<{}> {
-			return this.prompt(prompts).then(
-				(props: InquirerScaffoldObject): void => {
-					this.props = props;
-				}
-			);
+		public async prompting(): Promise<void> {
+			const scaffoldObject: InquirerScaffoldObject = await this.prompt(prompts);
+			this.props = scaffoldObject;
 		}
 
 		public default(): void {