OpenXml filter fails on Windows...

We have found some openxml documents fail on Windows (no issues on Linux) because Java still returns windows-1252 as the default charset. This cuases issues if the OpenXml document has a utf-8 encoding BOM or there are other encoding oddities.

The OpenXml filter depends on the default charset rather than specifying utf-8:

private Namespaces2 namespacesOf(final ZipEntry entry) throws IOException, XMLStreamException {
		try (final Reader reader = new InputStreamReader(this.generalDocument.inputStreamFor(entry))) {
			final Namespaces2 namespaces = new Namespaces2.Default(
					this.generalDocument.inputFactory()
			);
			namespaces.readWith(reader);
			return namespaces;
		}
	}

I think we should specify utf-8 in all cases as this is by far the most common encoding across platforms.