Update Spin Up Hub UI assets/links

[vdice]

Update the Spin Up Hub UI assets/links to navigate to its new home at spinframework.dev

Depends on

• update spinframework.dev to reflect docs in this repo spinframework/spin-docs#11
• feat: add fwf examples spinframework/spin-docs#47
• Spin Up Hub search not working spinframework/spin-docs#91

[vdice]

Noting that we'll potentially want to update the look of the cards in this section to indicate that clicking them will take the user to an external website (eg https://spinframework.dev/hub...)