Add proper page for account activation confirmation.

[Varunvaruns9]

Currently, we only show a text message telling the user that his account has been confirmed. Add a properly styled page with a link to the original website.

[dipanshu231099]

@kpbot claim

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[kpbot]

Hello @dipanshu231099, you have been unassigned from this issue because you have not updated this issue or any referenced pull requests for over 7 days.

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[Payalsahb20220]

@dipanshu231099 sir , I modify the account_activation html page .
please see my code if it is working properly or not.
also suggest some changes you want in my code.
Thank you.