[Customers Product]: Change references from 'User tracking' to 'Customers' 👥

[sumitramanga]

[Customers Product]: Change references from 'User tracking' to 'Customers' 👤

Description 📝

This PR is to updating the name convention for 'User tracking' to now be 'Customers' to reflect what's within the Raygun application.

NOTE: This is not to be merged until we have fully released the name change in the Raygun application

Updates
👉 Update README documentation
👉 Update sample app comment to refer to Customers

Test plan 🧪

• Make sure documentation changes are reflected to be 'Customers' instead of 'User Tracking'

Checklist ✔️

• Builds pass
• Reviewed by another developer
• Code is written to standards

[TheRealAgentK]

I wonder if we should avoid retrospectively changing the change log history.

[sumitramanga]

Is it better to bump the provider version stating that we've made documentation changes instead? 🤔

[TheRealAgentK]

Probably not necessary because all you've been doing here is changing terminology in documentation and it's done in a really clear way, I think. In the past I haven't bumped the version for doc improvements.

[TheRealAgentK]

I'll create a ticket for changing the public API to use customer as well, but that'll be a process of phasing it in and deprecating the old API over the next 2 releases.