fix: newsletter error feedback

[Balastrong]

Hey! I tried to signup to the newsletter but... nothing happened!
Turns out I was already registered but I didn't get any feedback from the page when I was trying to signup again.

I fixed a couple things there:

• If the email is invalid we set the border red, but this is visible only if the input is focused and it loses focus when you click the button -> now it refocuses the input if that's the case
• The waiting state (changing the button text and preventing further clicks) wasn't set
• I added an ugly alert to inform if the user is already registered or if a generic error happened.

Let me know what you think! I did 3 separate commits so if we want to keep some and discard others it's easy :)

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[TheJoin95]

Thanks for the improvement, looking good, merging

[Wabri]

Thanks @Balastrong the brightest star 🌟

[Balastrong]

Anything for the chairman @Wabri 😂