init monorepo

.gitignore

+node_modules/

CODEOWNERS.md

+packages/* @gakonst

README.md

+# Optimism Monorepo
+
+
+## Taming the Monorepo
+
+1. You solely use yarn workspaces for the Mono-Repo workflow.
+1. You use lerna’s utility commands to optimize managing of multiple packages, e.g., selective execution of npm scripts for testing.
+1. You use lerna for publishing packages since lerna provides sophisticated features with its version and publish commands.

lerna.json

+{
+  "npmClient": "yarn",
+  "useWorkspaces": true,
+  "packages": [
+    "packages/*"
+  ],
+  "version": "independent"
+}

package.json

+{
+  "name": "optimism",
+  "version": "1.0.0",
+  "main": "index.js",
+  "license": "MIT",
+  "workspaces": [
+    "packages/*"
+  ],
+  "private": true,
+  "devDependencies": {
+    "lerna": "^4.0.0"
+  },
+  "scripts": {
+      "postinstall": "lerna bootstrap --hoist"
+  }
+}

tsconfig.base.json

+{
+    "compilerOptions": {
+        "composite": true,
+        "module": "commonjs",
+        "target": "es2017",
+        "declaration": true,
+        "noImplicitAny": false,
+        "removeComments": true,
+        "noLib": false,
+        "emitDecoratorMetadata": true,
+        "experimentalDecorators": true,
+        "sourceMap": true,
+        "outDir": "./build",
+        "lib": [
+            "es7"
+        ],
+        "esModuleInterop": true,
+        "typeRoots": [
+            "node_modules/@types"
+      ]
+    }
+}

tslint.base.json

+{
+    "extends": [
+        "tslint:latest",
+        "tslint-config-prettier",
+        "tslint-plugin-prettier"
+    ],
+    "rulesDirectory": [
+        "tslint-no-focused-test"
+    ],
+    "rules": {
+        "ban-types": false,
+        "comment-format": false,
+        "interface-name": false,
+        "max-classes-per-file": false,
+        "member-ordering": false,
+        "no-console": false,
+        "no-bitwise": false,
+        "no-empty-interface": false,
+        "no-implicit-dependencies": [true, "dev"],
+        "no-string-literal": false,
+        "no-submodule-imports": false,
+        "no-unused-expression": false,
+        "object-literal-sort-keys": false,
+        "ordered-imports": false,
+        "semicolon": false,
+        "variable-name": false,
+        "no-focused-test": true,
+        "prettier": [true, "./prettier-config.json"]
+    },
+    "linterOptions": {
+        "exclude": [
+            "**/node_modules/**/*"
+        ]
+    } 
+}