Add Arthera Testnet to chains

packages/chains/src/artheraTestnet.ts

@@ -0,0 +1,20 @@
+import { Chain } from './types'
+
+export const artheraTestnet = {
+  id: 10243,
+  name: 'Arthera Testnet',
+  network: 'arthera-tesnet',
+  nativeCurrency: {
+    decimals: 18,
+    name: 'Arthera',
+    symbol: 'AA',
+  },
+  rpcUrls: {
+    default: { http: ['https://rpc-test.arthera.net'] },
+    public: { http: ['https://rpc-test.arthera.net'] },
+  },
+  blockExplorers: {
+    default: { name: 'Arthera Explorer', url: 'https://explorer-test.arthera.net/' },
+  },
+  testnet: true,
+} as const satisfies Chain