add a jsTSConfig to the rollup typescript plugin if no tsconfig is found

[dagda1]

Motivation

Fix for #959 where an annoying warning is displayed if no tsconfig.json exists

Approach

Add a js tsconfig.json if no tsconfig.json is found to the rollup typescript plugin.

This js tsconfig has the "allowJs": true compiler option set.

[changeset-bot]

🦋 Changeset detected

Latest commit: a8d513a

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

This PR includes changesets to release 2 packages

Name	Type
@bigtest/bundler	Minor
@bigtest/server	Patch

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Click here if you're a maintainer who wants to add another changeset to this PR

[github-actions]

The preview packages of this pull request have been published.
Click on the following packages for instructions on how to install them:

@bigtest/bundler

---

Install using the following command:

$ npm install @bigtest/bundler@allow-js

Or update your package.json file:

{
  "@bigtest/bundler": "allow-js"
}

---

@bigtest/project

---

Install using the following command:

$ npm install @bigtest/project@allow-js

Or update your package.json file:

{
  "@bigtest/project": "allow-js"
}

---

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