Added LinkValidation for formState.link in advertisementRegister

[Keshav-0907]

What kind of change does this PR introduce?
This pull request introduces a linkValidation() function to validate the link entered when creating an advertisement.

Issue Number:

Fixes #1479

Did you add tests for your changes?
No

Snapshots/Videos:

Untitled.mp4

If relevant, did you update the documentation?

No(not required)

Summary

Currently the user is allowed to input random strings or potentially invalid data in the formState.link. So, this PR fixes the issue by first validating if the formState.link is actually a link before creating a new advertisement.

Does this PR introduce a breaking change?

No

Other information

Have you read the contributing guide?
Yes

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