hardhat-deploy-config: Support JSON-formatted deploy configs (#3145)

Also adds a new `deployer` network for use with automation.

.changeset/fast-mangos-smoke.md

+---
+'@eth-optimism/hardhat-deploy-config': patch
+---
+
+Support JSON-formatted deploy configs

packages/contracts-bedrock/hardhat.config.ts

@@ -46,6 +46,11 @@ const config: HardhatUserConfig = {
       url: process.env.L1_RPC || '',
       accounts: [process.env.PRIVATE_KEY_DEPLOYER || ethers.constants.HashZero],
     },
+    deployer: {
+      chainId: Number(process.env.CHAIN_ID),
+      url: process.env.L1_RPC || '',
+      accounts: [process.env.PRIVATE_KEY_DEPLOYER || ethers.constants.HashZero],
+    },
   },
   foundry: {
     buildInfo: true,

packages/hardhat-deploy-config/src/plugin.ts

 import * as path from 'path'
+import * as fs from 'fs'
 
 import { extendEnvironment, extendConfig } from 'hardhat/config'
 import {
@@ -28,9 +29,16 @@ const normalizePath = (
 export const loadDeployConfig = (hre: HardhatRuntimeEnvironment): any => {
   let config: any
   try {
-    config =
+    const base = `${hre.config.paths.deployConfig}/${hre.network.name}`
+    if (fs.existsSync(`${base}.ts`)) {
       // eslint-disable-next-line @typescript-eslint/no-var-requires
-      require(`${hre.config.paths.deployConfig}/${hre.network.name}.ts`).default
+      config = require(`${base}.ts`).default
+    } else if (fs.existsSync(`${base}.json`)) {
+      // eslint-disable-next-line @typescript-eslint/no-var-requires
+      config = require(`${base}.json`)
+    } else {
+      throw new Error('not found')
+    }
   } catch (err) {
     throw new Error(
       `error while loading deploy config for network: ${hre.network.name}, ${err}`