Add support for multiple blocks directories

[ethanmay]

Related Issue/RFC: N/A

Description of the Change

This update enhances the 10up-toolkit integration to support local development workflows for shared block libraries. It adds support for using paths.blocksDir as an array, allowing multiple block source directories.

Alternate Designs

N/A

Possible Drawbacks

If there are blocks with identical names in both directories, it will result in build errors.

Verification Process

Tested the changes in my own WordPress environment using multiple block directories in separate locations. Added a test case to this PR.

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests passed.
• I have added a changeset to my PR. See CONTRIBUTING document for instructions

[changeset-bot]

🦋 Changeset detected

Latest commit: 32d80d8

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

This PR includes changesets to release 1 package

Name	Type
10up-toolkit	Minor

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