update paths to watch for handling multi-file OpenAPI docs

[mauris]

Implements #213

The bundle function in @redocly/openapi-core package provides the property fileDependencies, where it can be used to provide to Docusaurus through getPathsToWatch() a list of files to watch for changes because they are referenced from the main OpenAPI file through $ref references.

However changes to the list of files watched does not get updated by Docusaurus while running.

Test case:

1. Run the example site in dev using yarn dev
2. make changes in website/openapi/multi-file/components/pets.yaml
3. hot reload occurs and changes show up on example site

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🦋 Changeset detected

Latest commit: 5d64e44e9064e86ffd33b34d2f04029bf40405f7

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

| Name | Type | | ----------------------- | ----- | | docusaurus-plugin-redoc | Patch | | redocusaurus | Patch |

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Name	Status	Preview	Updated
redocusaurus	✅ Ready (Inspect)	Visit Preview	Jul 9, 2022 at 4:40PM (UTC)

[rohit-gohri]

However changes to the list of files watched does not get updated by Docusaurus while running.

That was easy enough to fix, I just added the spec file too. Thanks for the PR