Add info box before creating codespace: Enter details!

[agardnerIT]

We've had user feedback in other demos that (because GitHub cannot yet make secrets mandatory) it is easy to quickly scan the "form page" and for users just to click submit. Thus the scenarios spin up with missing critical info.

I've requested an enhancement with GitHub, but until then we need to protect against this.

• Step 1 will be to add a clear admonition / info box to the docs just before the "create a new codespace" instructions (a sample is given below)
• Step 2 perhaps will be to include a screenshot, making this even harder to miss
• Step 3 will be to add code-level checks into the spin-up code to "fail fast"

!!! info"Enter Required Information"
    During the next step you will be prompted for these details.

    Enter the relevant details in the GitHub form!