Add support for multiple configs to product picker

[herzog31]

• Add documentation to product picker
• Updated picker to support dedicated configuration files (configs.json, configs-stage.json and configs-dev.json).

Test URLs:

• Before: https://main--aem-boilerplate-commerce--hlxsites.hlx.live
• After: https://picker-configs--aem-boilerplate-commerce--hlxsites.hlx.live

[aem-code-sync[bot]]

Hello, I'm the AEM Code Sync Bot and I will run some actions to deploy your branch and validate page speed. In case there are problems, just click a checkbox below to rerun the respective action.

• [ ] Re-run PSI checks
• [ ] Re-sync branch

Commits

* [2e19135](https://github.com/hlxsites/aem-boilerplate-commerce/commit/2e191358264b96ca4a672cc6db5b8103492612be) :arrows_counterclockwise: (latest) * [a07e829](https://github.com/hlxsites/aem-boilerplate-commerce/commit/a07e829f312b6e3f744c4e2854b0754fd86598d3) :white_check_mark:

[aem-code-sync[bot]]

	Page	Scores	Audits	Google
:iphone:	/
:desktop_computer:	/