Update README.md

Author: oozcitak

README.md

@@ -104,6 +104,6 @@ This will result in:
 See the [wiki](https://github.com/oozcitak/xmlbuilder-js/wiki) for details and [examples](https://github.com/oozcitak/xmlbuilder-js/wiki/Examples) for more complex examples.
 
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+Please consider becoming a backer or sponsor to help support development.
 
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