Add script to print VSIX path after packaging the extension

package.json

@@ -9,7 +9,8 @@
 		"build": "yarn build-data-extraction && yarn build-ui && yarn build-extension",
 		"build-data-extraction": "yarn workspace @hediet/debug-visualizer-data-extraction build",
 		"build-ui": "yarn workspace debug-visualizer-webview build",
-		"build-extension": "yarn workspace debug-visualizer build"
+		"build-extension": "yarn workspace debug-visualizer build",
+		"package": "yarn build && yarn workspace debug-visualizer package && node print-vsix-path.js"
 	},
 	"devDependencies": {
 		"prettier": "^2.8.8"

print-vsix-path.js

@@ -0,0 +1,13 @@
+// Run after `yarn workspace debug-visualizer package` -- vsce's own stdout
+// ("DONE Packaged: ...") isn't meant to be parsed programmatically, so this
+// just checks the fixed -o path that extension/package.json's own "package"
+// script passes to vsce, and prints it (or fails loudly if it's missing).
+const fs = require("fs");
+const path = require("path");
+
+const vsixPath = path.resolve(__dirname, "extension", "dist", "extension.vsix");
+if (!fs.existsSync(vsixPath)) {
+	console.error("Expected .vsix not found at " + vsixPath);
+	process.exit(1);
+}
+console.log(vsixPath);