fix: Ensuring the sw flag is a boolean in watch mode

Author: rschristian

.changeset/tender-carrots-sniff.md

@@ -0,0 +1,5 @@
+---
+'preact-cli': patch
+---
+
+Ensuring the sw flag is a boolean in watch mode

packages/cli/lib/commands/watch.js

@@ -2,6 +2,8 @@ const runWebpack = require('../lib/webpack/run-webpack');
 const { warn } = require('../util');
 const { validateArgs } = require('./validate-args');
 
+const toBool = val => val === void 0 || (val === 'false' ? false : val);
+
 const options = [
 	{
 		name: '--src',
@@ -101,6 +103,7 @@ async function command(src, argv) {
 	}
 	argv.src = src || argv.src;
 	argv.production = false;
+	argv.sw = toBool(argv.sw);
 
 	if (argv.https || process.env.HTTPS) {
 		let { key, cert, cacert } = argv;