fix: resolve external references in base file

[Souvikns]

Description
A small fix for asyncapi/cli#391, the external references from the base file were not being resolved, This PR adds -

• external reference resolution for base file
• tests for base file file usage.

Related issue(s)

Fixes #101

[aeworxet]

Jest test in Bundler's repository was passing both WITHOUT and WITH the proposed change, so the CLI repository had to be used.

In root of CLI repository executed

$ npm run build

then ran

$ ./bin/run bundle ./test/commands/bundle/asyncapi.yaml ./test/commands/bundle/spec.yaml --reference-into-components -b ./test/commands/bundle/asyncapi.yaml -o ./test/commands/bundle/main.yaml

Visual diff of the code WITHOUT and WITH proposed change:

[aeworxet]

/rtm

[asyncapi-bot]

Hello, @aeworxet! 👋🏼
This PR is not up to date with the base branch and can't be merged.
Please update your branch manually with the latest version of the base branch.
PRO-TIP: Add a comment to your PR with the text: /au or /autoupdate and our bot will take care of updating the branch in the future. The only requirement for this to work is to enable Allow edits from maintainers option in your PR.
Thanks 😄

[aeworxet]

/autoupdate

[asyncapi-bot]

🎉 This PR is included in version 0.3.8 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀