Fix ORAI base denom and add images (cosmos#341)

* Fix ORAI base denom

should be 'uorai', not 'orai'

* Oraichain: add logo to repo

* Oraichain: fix base, and denom/display case

Author: zhongfu

oraichain/assetlist.json

@@ -6,21 +6,21 @@
       "description": "The native token of Oraichain",
       "denom_units": [
         {
-          "denom": "orai",
+          "denom": "uorai",
           "exponent": 0
         },
         {
-          "denom": "ORAI",
+          "denom": "orai",
           "exponent": 6
         }
       ],
-      "base": "orai",
+      "base": "uorai",
       "name": "Oraichain",
-      "display": "ORAI",
+      "display": "orai",
       "symbol": "ORAI",
       "logo_URIs": {
-        "png": "https://orai.io/images/logos/logomark-dark.png",
-        "svg": "https://orai.io/images/logos/logomark-dark.svg"
+        "png": "https://raw.githubusercontent.com/cosmos/chain-registry/master/oraichain/images/orai.png",
+        "svg": "https://raw.githubusercontent.com/cosmos/chain-registry/master/oraichain/images/orai.svg"
       },
       "coingecko_id": "oraichain-token"
     }