web-installer: add a note for fairphone users for oem unlock steps

Description

Currently, for Fairphone devices, enable oem unlocking step in web-installer is missing part where user has to request for unlock code from Fairphone bootloader unlock page.
Add a warning section under OEM Unlock step to notify Fairphone users to follow steps in our documentation.

Screenshots

Technical details

Requires documentation side PR:
https://gitlab.e.foundation/e/documentation/user/-/merge_requests/1360

Tests

• npn run dev to preview webpage
• Visit http://localhost:5173
• Confirm warning is present in OEM Unlock section

Issues

https://gitlab.e.foundation/e/devices/backlog/-/issues/1517

10 commandments of code review

👪 ❤️ code review guidelines