license: add FB License header to all extractErrors code

- this plugin is largely borrowed from the React monorepo, consistently
  add FB's License headers to each file, not just to extractErrors.ts

- also add comments pointing to the exact file and commit that each
  file was copied from
  - most of these are slightly out of date now:
    - evalToString is missing a line
    - extractErrors needs to be updated to Babel 7
      - babylon -> @babel/parser, babel-traverse -> @babel/traverse
    - transformErrorMessages has several new constructs added :/...
      - keeping a pseudo-fork up-to-date is pretty tedious and not very
        maintainble (it's also broken per the tests I've added)
        - would be better if we could ask FB to split out theirs as a
          separate package...

src/errors/evalToString.ts

@@ -1,3 +1,11 @@
+// largely borrowed from https://github.com/facebook/react/blob/8b2d3783e58d1acea53428a10d2035a8399060fe/scripts/shared/evalToString.js
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 export function evalToString(ast: any): string {
   switch (ast.type) {
     case 'StringLiteral':

src/errors/extractErrors.ts

@@ -1,3 +1,4 @@
+// largely borrowed from https://github.com/facebook/react/blob/8b2d3783e58d1acea53428a10d2035a8399060fe/scripts/error-codes/extract-errors.js
 /**
  * Copyright (c) Facebook, Inc. and its affiliates.
  *

src/errors/invertObject.ts

@@ -1,3 +1,12 @@
+// largely borrowed from https://github.com/facebook/react/blob/8b2d3783e58d1acea53428a10d2035a8399060fe/scripts/error-codes/invertObject.js
+
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 /**
  * turns
  *   { 'MUCH ERROR': '0', 'SUCH WRONG': '1' }

src/errors/transformErrorMessages.ts

@@ -1,3 +1,11 @@
+// largely borrowed from https://github.com/facebook/react/blob/2c8832075b05009bd261df02171bf9888ac76350/scripts/error-codes/transform-error-messages.js
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
 import fs from 'fs';
 import { invertObject } from './invertObject';
 import { evalToString } from './evalToString';