Add storybookBaseDir to Chromatic workflow

[joecowton1]

What are you changing?

• adding a storybookBaseDir to the Chromatic workflow.

Why?

• each of the individual storybooks is nested within libs/@guardian/[projectName], we need to tell chromatic where to find these.
• Many thanks to Reuben at Chromatic for suggesting this fix.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 1e8522e

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

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