Add custom alerts

[amin-xiv]

Description

Added custom alerts, for the signup and login page. And I found out that there are similar functions that are needed on the main, login and signup page, therefore I moved them to a file called sharedUtilities.js, in which they are stored and used by simply importing them. This new file isn't only limited to this use, but it can be used for almost anything in the future. I also removed the <script> tag linking to the script.js file in the login page, since it wasn't doing much there, and might even cause some conflicts in the future. I tested everything, everything is working as I expected, across the three pages. (index, signup and login).

Related Issue

Fixes #341

Type of change

• Bug fix
• New feature

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented on my code, particularly in hard-to-understand areas
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[github-actions]

🎉 Thank you for your contribution! Your pull request has been submitted successfully. A maintainer from team will review it as soon as possible. We appreciate your support in making Dataverse better.

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[github-actions]

🎉🎉 Thank you for your contribution! Your PR #346 has been merged! 🎉🎉