fix: preview form data payload in a table

[e-fisher]

Reported by Tom:

application/x-www-form-urlencoded POST data are being rendered as JSON in the payload tab. Ideally they would appear much like how we render headers i.e. table style

Render x-www-form-urlencoded payload as table

Before:

After

[e-fisher]

Previously, the function would return any and typescript didn't recognize the return value could be undefined

[Llandy3d]

🚀

[e-fisher]

Merging this with one approval since my next task depends on it, @going-confetti feel free to comment if something doesn't look right, and I'll address it in a separate PR