caxlsx: Package#to_stream does not work in 3.2.0

Hello 👋

I’ve noticed that since the update to v3.2.0, Package#to_stream method stopped working. I suspect the issue is due to this change:

v3.2.0

package = Axlsx::Package.new
package.to_stream.external_encoding
=> #<Encoding:ASCII-8BIT>

While in the previous version, the encoding was UTF-8:

package = Axlsx::Package.new
package.to_stream.external_encoding
=> #<Encoding:UTF-8>

When I try to write the stream to the file (as per the docs) I get the following error:

Encoding::UndefinedConversionError: "\xEC" from ASCII-8BIT to UTF-8

Since this issue was a breaking change for me, I believe it should’ve been stated as such in the Changelog.md

Btw I’ve switched to using Package#serialize in the meantime and it is working. 🙂