This needs integration with a couple of bits of the web platform:

• Web IDL's ArrayBufferView, BufferRelatedType, etc need to be updated to list Float16Array done in Add Float16Array whatwg/webidl#1398
• WebGL's texImage2D needs to be updated so Float16Array is accepted as a source for HALF_FLOAT

As far as I am aware these are the only places which need updating currently (updating Web IDL will flow to a number of places, including WebGPU). WebNN and float-backed canvases are in progress features, and I've informed people working on both about Float16Array.