Add OXML to XML parsers/builders

[xkwd]

Hello and thank you for maintaining the Ruby Toolbox! 🎉

I have recently developed an XML parser/builder with improved performance for commercial purposes, but now I have a chance to share it with the community. I often use your catalog for development and thought it might be a good idea to spread the word about the OXML gem here. I hope this is appropriate and would appreciate your approval 🙂 Thanks!

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[colszowka]

Thanks @xkwd 👍