test: Add a test harness for the built card (#2653)

Mounts the card from `dist/` the way Home Assistant does, by URL with a
HACS tag, and asserts the entry stays a facade, that no chunk imports
it, that the browser is served the file unmodified, and that the card
starts up and fetches a language chunk lazily.

Runs in Chromium, Firefox and WebKit, so a change of bundler or minifier
is checked against every engine.

src/const.ts

@@ -15,6 +15,13 @@ export const TROUBLESHOOTING_LEGACY_RESOURCE_URL =
 export const TROUBLESHOOTING_MEDIA_URL =
   `${TROUBLESHOOTING_URL}?id=media-unavailable` as const;
 
+// ===========================================================================
+// Interaction Constants
+// ===========================================================================
+
+// How long a press must last to count as a hold rather than a tap.
+export const ACTION_HANDLER_HOLD_SECONDS = 0.4;
+
 // ===========================================================================
 // Media Constants
 // ===========================================================================