Update makepot process to include build js strings

[alexiglesias31]

All Submissions:

• Does your code follow the Extendables standards?
• Have you written new tests for your changes, as applicable?
• Have you successfully run tests with your changes locally?

Changes proposed in this Pull Request:

Improve the flows to generate the .pot file to include the translatable strings used on Checkout Blocks.

How to test the changes in this Pull Request:

1. Install a build of this branch.
2. The strings on Checkout Blocks should be translated (e.g. "Proceed to Amazon")

Changelog entry

Fix - Translate strings used on Checkout Blocks.

[Greg36]

Looks good! I've checked the diff on the pot file and it looks correct.