Post install message, Hollywood-sign style

[DannyBen]

I love ascii-art as much as the next guy, but doesn't this set a dangerous precedence?
Can you imagine all gems would do something like this?

As I understand it, the original intention of this hook was only for extremely critical, short messages.

Post-install message from sidekiq:

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  █████████  █████ ██████████   ██████████ █████   ████ █████    ██████       ██████████       █████
 ███░░░░░███░░███ ░░███░░░░███ ░░███░░░░░█░░███   ███░ ░░███   ███░░░░███    ░███░░░░███     ███░░░███
░███    ░░░  ░███  ░███   ░░███ ░███  █ ░  ░███  ███    ░███  ███    ░░███   ░░░    ███     ███   ░░███
░░█████████  ░███  ░███    ░███ ░██████    ░███████     ░███ ░███     ░███         ███     ░███    ░███
 ░░░░░░░░███ ░███  ░███    ░███ ░███░░█    ░███░░███    ░███ ░███   ██░███        ███      ░███    ░███
 ███    ░███ ░███  ░███    ███  ░███ ░   █ ░███ ░░███   ░███ ░░███ ░░████        ███       ░░███   ███
░░█████████  █████ ██████████   ██████████ █████ ░░████ █████ ░░░██████░██      ███      ██ ░░░█████░
 ░░░░░░░░░  ░░░░░ ░░░░░░░░░░   ░░░░░░░░░░ ░░░░░   ░░░░ ░░░░░    ░░░░░░ ░░      ░░░      ░░    ░░░░░░


1. Use `gem 'sidekiq', '<7'` in your Gemfile if you don't want this new version.
2. Read the release notes at https://github.com/mperham/sidekiq/blob/main/docs/7.0-Upgrade.md
3. Search for open/closed issues at https://github.com/mperham/sidekiq/issues/

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[mperham]

This was done so people who installed 7.0 wouldn't be confused if suddenly things started blowing up.

We can remove the art now that we're past the initial release window.