WIT.md grammatical production for `resource-item` not defined

[esoterra]

No production rule or definition exists for the resource-item term.

[lukewagner]

Hah, yeah, it was added when there was prototype support in wit-bindgen and removed when that prototype support was removed in anticipation of the current proposed resources/handles. It should be re-added fairly soon, but happy to remove the dangling reference in the interim.

[esoterra]

Resolved by #206