[CALCITE-1142] Create a README for Avatica
[CALCITE-1142] Create a README for Avatica

apache/calcite-avatica,dindin5258/calcite,dindin5258/calcite,b-slim/calcite,xhoong/incubator-calcite,jcamachor/calcite,datametica/calcite,arina-ielchiieva/calcite,vlsi/incubator-calcite,adeshr/incubator-calcite,dindin5258/calcite,adeshr/incubator-calcite,yeongwei/incubator-calcite,arina-ielchiieva/calcite,looker-open-source/calcite-avatica,amoghmargoor/incubator-calcite,datametica/calcite,arina-ielchiieva/calcite,vlsi/calcite,minji-kim/calcite,looker-open-source/calcite-avatica,minji-kim/calcite,apache/calcite,apache/calcite,xhoong/incubator-calcite,yeongwei/incubator-calcite,wanglan/calcite,wanglan/calcite,xhoong/incubator-calcite,wanglan/calcite,looker-open-source/calcite-avatica,vlsi/calcite,googleinterns/calcite,amoghmargoor/incubator-calcite,datametica/calcite,apache/calcite-avatica,sreev/incubator-calcite,minji-kim/calcite,jcamachor/calcite,b-slim/calcite,yeongwei/incubator-calcite,adeshr/incubator-calcite,jcamachor/calcite,googleinterns/calcite,minji-kim/calcite,dindin5258/calcite,apache/calcite,joshelser/calcite-avatica,hsuanyi/incubator-calcite,apache/calcite-avatica,looker-open-source/calcite-avatica,joshelser/calcite-avatica,looker-open-source/calcite,hsuanyi/incubator-calcite,apache/calcite-avatica,jcamachor/calcite,b-slim/calcite,adeshr/incubator-calcite,dindin5258/calcite,wanglan/calcite,looker-open-source/calcite,datametica/calcite,xhoong/incubator-calcite,sreev/incubator-calcite,apache/calcite,apache/calcite,googleinterns/calcite,datametica/calcite,googleinterns/calcite,apache/calcite,apache/calcite-avatica,looker-open-source/calcite,dindin5258/calcite,looker-open-source/calcite,arina-ielchiieva/calcite,amoghmargoor/incubator-calcite,datametica/calcite,sreev/incubator-calcite,b-slim/calcite,looker-open-source/calcite,amoghmargoor/incubator-calcite,googleinterns/calcite,julianhyde/calcite,julianhyde/calcite,b-slim/calcite,jcamachor/calcite,minji-kim/calcite,julianhyde/calcite,googleinterns/calcite,looker-open-source/calcite,hsuanyi/incubator-calcite,vlsi/calcite,arina-ielchiieva/calcite,sreev/incubator-calcite,joshelser/calcite-avatica,julianhyde/calcite,vlsi/incubator-calcite,vlsi/calcite,yeongwei/incubator-calcite,julianhyde/calcite,jcamachor/calcite,julianhyde/calcite,hsuanyi/incubator-calcite,looker-open-source/calcite-avatica,vlsi/calcite,vlsi/calcite