feat(ux): tips on startup

[imsnif]

This adds 12 unique Zellij usage tips that will appear when a session start, and can be browsed or dismissed.

It's possible to disable them through the config by adding show_startup_tips false to the Zellij configuration, or through the tips themselves by pressing Ctrl c - which will add this line to the config for you.

Some samples:

[Lockszmith-GH]

I love it.
I see the shortcut keys are hard coded, so if I change ctrl + g to something else, the tip is no longer relevant.
When it's me making changes to my own setup, that's fine - but if I help setup an environment for someone who is new to zellij, then the tips might be wrong if I used my own configuration (which is what they want, as they played with it on my machine)

[imsnif]

Thanks, I hope to add the ability to customize these in the future!