Add rotating block-specific tips to the inserter's help panel

[kjellr]

We should add block-specific tips in the inserter panel that was added in #16813. These could be defined in the block registration. For example:

const blockSettings = {
    // ... other settings

    tips: [
        'Quickly indent the text in a new list item by starting it with a space.',
    ]
}

If defined there, we may also consider placing these elsewhere in the UI: perhaps in the Block Sidebar (#16594) or the Block Placeholder (#16315). But the inserter is a good first step. 👍

To start, we can pull from the list of block-specific tips listed in #16595 (comment). In cases where there are multiple tips per block, we'll randomly chose one to display each time the block is hovered.

Example screenshot:

[gracie]

We're working on getting specific ideas for this issue here..

I'm excited about the initiative. In looking at the UI mock-up, I'm concerned the text will be ignore-able. It's small, largely black and white, and I didn't catch the lightbulb at the bottom until I looked for it.

I'm sorry for the critique without an alternative. Do you have ideas for how to make it stand out and catch a new user's eye to pay attention to it?

[richtabor]

This is a great idea @kjellr and something worth getting some action on. I'm looking forward to these!