ERROR No translation found for %abc%

[tamuratak]

vsce v2.26.1 raises ERROR No translation found for %abc% when executing vsce package.

Steps to reproduce:

1. Add the following to package.json of the extension:

	"contributes": {
		"configuration": {
			"title": "Hello World",
			"type": "object",
			"properties": {
				"someString": {
					"type": "string",
					"default": "%abc%"
				}
			}
		}
	},

2. Execute vsce package.

vsce should not validate the default values of configurations, which can be any value.

[benibenj]

It seems like translations are validated even when there is no NLS file. I changed it such that NLS validation only happens when a NLS file is present

[benibenj]

verification by code review: https://github.com/microsoft/vscode-vsce/pull/983/files