Fix incompatibility issue between ES6 Promise and Bluebird in Typescript definitions

[snnsnn]

📝 Description

I added async started and stopped functions to my service schema but Typescript gives the error below:

import http from 'http';
import { ServiceSchema } from 'moleculer';

const serviceSchema: ServiceSchema = {
  name: 'www',

  settings: {
    port: 3000,
  },

  created() {
    this.server = http.createServer(this.httpHandler);
  },

  async started() {
    this.server.listen(this.settings.port);
  },

  async stopped() {
    this.server.close();
  },

  methods: {
    httpHandler(req: any, res: any) {
      res.end('Hello Moleculer!');
    },
  },
};

Here is the ts error:

Type '() => Promise<void>' is not assignable to type '() => Bluebird<void>'.
  Type 'Promise<void>' is not assignable to type 'Bluebird<void>'.
    Property 'caught' is missing in type 'Promise<void>'.
Type '() => Promise<void>' is not assignable to type '() => Bluebird<void>'.
  Type 'Promise<void>' is not assignable to type 'Bluebird<void>'.

Bluebird itself implements PromiseLike interface, so I thought It would be good choice to use PromiseLike instead of Bluebird to remove incompatibility. Or we could use union type, maybe?

🎯 Relevant issues

💎 Type of change

• Bug fix (non-breaking change which fixes an issue)
• This change requires a documentation update

🏁 Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code

[coveralls]

Pull Request Test Coverage Report for Build 1627

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.01%) to 92.277%

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Totals
Change from base Build 1622:	0.01%
Covered Lines:	4721
Relevant Lines:	4894

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💛 - Coveralls

[icebob]

@faeron @rmccallum81 @ryanm-pm please review it.

[icebob]

Thank you