Leave browser zoom to the browser (#578)

The web build bound Cmd/Ctrl +, - and 0 and then did nothing with them, so zoom appeared broken. Those keys are the browser's own page zoom, which scales the whole page and remembers it per site.

Adds an interfaceZoom capability: true on desktop, where the host zooms the webview, false in a browser. When false the app binds nothing and the hotkeys screen drops the three rows it can't configure.

packages/platform/src/web/index.ts

@@ -52,6 +52,9 @@ function capabilitiesFor(): PlatformCapabilities {
     // The browser draws the frame around the page. There are no traffic lights
     // to leave room for and no window controls to draw.
     windowChrome: false,
+    // The browser already zooms the page, on the same keys, and remembers it
+    // per site. The app stays out of the way.
+    interfaceZoom: false,
     plugins: false,
     encryption: false,
     updater: false,