Prior to this change, the `Invoke-WebRequest` and `Invoke-RestMethod`
cmdlets in 7.0.0 and higher included the **SkipHeaderValidation**
parameter but not a specific example showing its use.

This change adds a new example for both cmdlets to show:

- How the cmdlets behave when an invalidly formatted value is specified
  for a header that has validation
- How the cmdlets behave when the value is valid
- How the **SkipHeaderValidation** parameter allows users to use values
  that would normally fail validation.

This change also updates the formatting for the updated files to ease
future maintenance.