Add sample to demonstrate bulk email send with optional throttling policy.

[apattath]

Purpose

This change adds an additional sample to SendMailAdvanced solution to demonstrate how to send emails in bulk and optionally add a custom throttling policy handler.

• ...

Does this introduce a breaking change?

[ ] Yes
[X] No

Pull Request Type

What kind of change does this Pull Request introduce?

[ ] Bugfix
[X] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:

How to Test

• Get the code

git clone [repo-address]
cd [repo-name]
git checkout [branch-name]
npm install

• Test the code

What to Check

Verify that the following are valid

• ...

Other Information