add rubygem version badge
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yang7229693/synx,cnbin/synx,superboonie/synx,0x73/synx,venmo/synx,pxpgraphics/synx,fabiojgrocha/synx,orta/synx,sidorov-panda/synx,LiuDeng/synx,jerrywell/synx,zhigang1992/synx,rowliny/synx