[release] webpack.config.js: ignore warnings from yargs dependency

The dependency on 'yargs-parser' and 'yargs-unparser' broke the
webpack. The recommended fix from yargs/yargs#781
is to filter out the warnings in the webpack config.

Manually tested by running `vsce-package`.

Change-Id: Ia0115fd0ccf4a5edfddef4b8f020a70a7e6720a0
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/272093
Trust: Suzy Mueller <suzmue@golang.org>
Trust: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Suzy Mueller <suzmue@golang.org>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/272446
Reviewed-by: Heschi Kreinick <heschi@google.com>
Reviewed-by: Peter Weinberger <pjw@google.com>

Author: suzmue

webpack.config.js

@@ -44,5 +44,9 @@ const config = {
 		// when this is true, the debugger breaks...
 		minimize: false
 	},
+	stats: {
+		// Ignore warnings due to yarg's dynamic module loading
+		warningsFilter: [/node_modules\/yargs/]
+	},
 };
 module.exports = config;