Add eslint config

.eslintrc.js

@@ -26,6 +26,14 @@ module.exports = {
     semi: ["error", "always"],
     "spaced-comment": ["error", "always", { exceptions: ["-", "+"] }],
     "no-console": 0,
+    "no-restricted-imports": [
+      "error",
+      {
+        "paths": [
+          { name: "ethers", importNames: ["BigNumber"], message: "Use 'src/utils/BigNumberUtils' instead" },
+        ]
+      }
+    ],
     "@typescript-eslint/no-unused-vars": ["error", { ignoreRestSiblings: true }],
     "chai-expect/missing-assertion": 2,
     "no-duplicate-imports": "error",

e2e/oracle.e2e.ts

@@ -1,8 +1,9 @@
 // @note: This test is _not_ run automatically as part of git hooks or CI.
 import dotenv from "dotenv";
 import winston from "winston";
-import { BigNumber, providers, utils as ethersUtils } from "ethers";
+import { providers, utils as ethersUtils } from "ethers";
 import { getGasPriceEstimate } from "../src/gasPriceOracle";
+import { BigNumber } from "../src/utils";
 import { assertPromiseError, expect } from "../test/utils";
 dotenv.config({ path: ".env" });