Documentation: Kubernetes Object Capitalization and Gateway Field Formatting

[ja20222]

As a user of NGINX Kubernetes Gateway
I want the NKG documentation to capitalize Kubernetes objects
So that the documentation is easier to read and I can make the the connection between what is discussed and the specific Kubernetes implementation.

Acceptance

• Whenever a Kubernetes object is referred to in NKG documentation, that object name is capitalized.
• Gateway fields should use ` to denote we are referring to a specific field that the user can change.