Intent to prototype: Float16Array

[Daniel Minor]

Summary: Float16Array is a new typed array analogous to existing typed arrays like Float32Array. Float16 is widely used for GPU computation in applications where speed and memory use are more important than precision; having Float16Array in JavaScript will facilitate passing data to the GPU.

Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1833646

Specification: https://github.com/tc39/proposal-float16array

Standards Body: TC39

Platform coverage: all

Preference: javascript.options.experimental.float16array

DevTools bug: n/a

Link to standards-positions discussion: n/a

Other browsers:

• Blink: https://bugs.chromium.org/p/v8/issues/detail?id=14012
  
• WebKit: https://bugs.webkit.org/show_bug.cgi?id=257022

web-platform-tests: Coverage in test262, e.g. https://github.com/tc39/test262/blob/e4f91b6381d7694265031caad0c71d733ac132f3/harness/testTypedArray.js#L35