README: Add Web API motivation (#3)

Fixes #2

Author: gibson042

README.md

@@ -36,6 +36,8 @@ Both a `DataView` object and a `TypedArray` object are views into a buffer backi
 
 Some JavaScript implementations, like Moddable XS, bring JavaScript to embedded systems, like device controllers, where ROM is much more plentiful and cheaper than RAM. These systems need to place voluminous fixed data into ROM, and currently do so using semantics outside the official JavaScript standard.
 
+APIs that accept ArrayBuffers and/or objects backed by them could also benefit from performance improvement by avoiding defensive copies when the input buffers are immutable (see [Generic zero-copy ArrayBuffer usage](https://gist.github.com/domenic/a9343fa787ba54b4ba3a60882c49cc32) for a proposed alternative solution to this problem in the Web Platform).
+
 The [OCapN](https://ocapn.org/) network protocol treats strings and byte-arrays as distinct forms of bulk data to be transmitted by copy. At JavaScript endpoints speaking OCapN such as [@endo/pass-style](https://www.npmjs.com/package/@endo/pass-style) + [@endo/marshal](https://www.npmjs.com/package/@endo/marshal), JavaScript strings represent OCapN strings. The immutability of strings in the JavaScript language reflects their by-copy nature in the protocol. Likewise, to reflect an OCapN byte-array well into the JavaScript language, an immutable container of bulk binary data is required. There currently are none, but an Immutable `ArrayBuffer` would provide exactly the necessary low-level machinery.
 
 ## Solution