80% reduction in .wasm asset size

[texodus]

WASM assets gzip quite well when properly configured on your application's HTTP server via the Content-Encoding: gzip header, and you can even remove the on-the-fly gzip cost by pre-zipping the wasm and configuring your server appropriately, but

• Content-Encoding: gzip doesn't affect the perceived size of the perspective inline (e.g. without the webpack-plugin) builds, especially in the developer's imagination (see Consume perspective with esbuild #1655). Also, the inlined base64 WASM payload as a string does not compress nearly as well as gzipping the original WASM.
• CDNs generally don't recognize pre-gzipped assets (as they likely shouldn't).
• Even with the build plugin, WASM assets sizes are large and perspective's build is complex enough without asking app developers to provide bespoke server support.

To mitigate this perception/complexity, this PR gzips Perspective's WASM assets during the build step, then uses fflate, a small (3kb) gzip Javascript library, to unzip the WASM content in Perspective's JavaScript client after downloading. The result is nearly 80% reduction in Perspective WASM asset size without the use of Content-Encoding, at the cost of a few ms of additional startup time (with a margin of error at 400ms+ on my tests).

• umd/perspective.js inline single-JS build, 8.0mb -> 1.7mb
• cdn/perspective.cpp.wasm plugin build, 6.0mb -> 1.3mb
• cdn/perspective-viewer.js inline single-JS build, 4.2mb -> 3.2mb (most of this is monaco)
• cdn/perspective_viewer_bg.wasm plugin build, 1.2mb -> 300kb