Add Across config validation on CI pipeline (#61)

### What was the problem?

This PR resolves LISK-899.

### How was it solved?

PR pipeline was updated to validate 

### How was it tested?

Tested locally with `yarn validate-config` with valid and invalid
configs.

.github/workflows/pr.yaml

@@ -30,4 +30,8 @@ jobs:
             echo "Running format is required"
             exit 1
           fi
-      - run: yarn test
+      - name: Validate configuration
+        run: yarn validate-config
+      - name: Test
+        shell: bash
+        run: yarn test

package.json

@@ -55,6 +55,7 @@
     "lint-fix": "yarn eslint --fix && yarn prettier --write",
     "format": "prettier --write '**/*'",
     "eslint": "eslint .",
+    "validate-config": "yarn ts-node ./scripts/validateConfig.ts",
     "test": "RELAYER_TEST=true hardhat test",
     "build": "tsc --build",
     "watch": "tsc --build --incremental --watch",

scripts/validateConfig.ts

@@ -0,0 +1,34 @@
+import { RelayerConfig } from "../src/relayer/RelayerConfig";
+
+// Example run:
+// ts-node ./scripts/validateConfig.ts
+
+export async function run(): Promise<void> {
+  console.log("Validating config");
+
+  const env: NodeJS.ProcessEnv = {
+    RELAYER_TOKENS:
+      '["0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2", "0x6033F7f88332B8db6ad452B7C6D5bB643990aE3f", "0xdAC17F958D2ee523a2206206994597C13D831ec7"]',
+    MIN_DEPOSIT_CONFIRMATIONS:
+      '{"5000": { "1": 5, "1135": 10 }, "2000": { "1": 4, "1135": 10 }, "100": { "1": 3, "1135": 10 } }',
+    RELAYER_ORIGIN_CHAINS: JSON.stringify([1, 1135]),
+    RELAYER_DESTINATION_CHAINS: JSON.stringify([1, 1135]),
+    RELAYER_EXTERNAL_INVENTORY_CONFIG: "config/mainnet/relayerExternalInventory.json",
+  };
+  new RelayerConfig(env);
+
+  console.log("Config is valid");
+}
+
+if (require.main === module) {
+  run()
+    .then(async () => {
+      // eslint-disable-next-line no-process-exit
+      process.exit(0);
+    })
+    .catch(async (error) => {
+      console.error("Process exited with", error);
+      // eslint-disable-next-line no-process-exit
+      process.exit(1);
+    });
+}