[Update] PR Template to add design example

[aditikum]

Description

Adding section to PR Template requiring all new features to also have a link to the design example.
This will help document new features for both internal and external contributions.

Collateral (docs, reports, design examples, case IDs):

• Document Update Required? (Specify FIM/AFU/Scripts)

Tests added:

N/A

Tests run:

N/A

[cohensus]

all new features may not have an entire design example. Maybe you want to say:

• All new features must have a corresponding working example of how to use the feature. Add link to example here (can be new or existing):