Replace hard coded strings with custom labels

The reference implementation code has hard coded strings everywhere. The Salesforce recommended best practice is to use Custom Labels instead, since they are translatable and editable through configuration (no need for code changes).

Currently, if a customer admin wants to change text from one of the quick start pages after it has been deployed, they would need to edit the LWC code (not an admin function). If the quickstart code was written with Salesforce best practices to not hard code strings, the admins would only just need to edit a custom label.

Because hard coded strings are used everywhere in the quickstart, and the quickstart is used for all custom PLP/PDP pages as a starting point, it is likely that Salesforce customers are being delivered less maintainable implementations with hard coded strings.