docs: README updated for Creating App registration

[Roopan-Microsoft]

Purpose

• README updated for creating the App registration if user is not able to add Identity provider under app service.
• They can create the App Registration and then link it.

Does this introduce a breaking change?

• Yes
• No

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

[github-actions]

Coverage Report •

File	Stmts	Miss	Cover	Missing
TOTAL	3109	915	70%

report-only-changed-files is enabled. No files were changed during this commit :)

Tests	Skipped	Failures	Errors	Time
301	0 💤	0 ❌	0 🔥	48.908s ⏱️

[github-actions]

🎉 This PR is included in version 1.12.3 🎉

The release is available on GitHub release

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