Renames Build folder to Developers

[dawnkelly09]

What? Change name of Build section to Developers

Why? Align with revamped Filecoin developer docs section

How? Edits on lines 27-29 to name and url (will edit [[build]] entries under separate PR)

Testing? N/A

Screenshots (optional) N/A

Anything Else? Still sorting out Hugo but this should only change the "Build" appearing in the top navbar to read "Developers". If it does anything else, please ping me so I can try again!