Update Dockerfile to use MCR image

[dlepow]

Purpose

Substitutes dotnet core image from Microsoft Container Registry to replace image from Docker Hub. All Microsoft images should be pulled from MCR

Does this introduce a breaking change?

[ ] Yes
[x ] No

Pull Request Type

What kind of change does this Pull Request introduce?

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

No breaking changes expected. Retesting is recommended to confirm

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

If you have questions about this change, please reach out to danlep (MSFT alias). Thank you.