refactor!: move dist/module to lib and export flow types

Moving esm files to `lib/` folder gives us a path to stop importing from
`src/` when importing files for treeshaking. We can migrate to importing
from `lib/` and still have flow definitions at the ready

Tasks Completed:
- Remove module folder
- Output transpiled code and flow defs to `lib/`

lib/constants.js.flow

@@ -0,0 +1,14 @@
+/* @flow */
+
+export const PROTOCOL = {
+    MOCK:  ('mock:' : 'mock:'),
+    FILE:  ('file:' : 'file:'),
+    ABOUT: ('about:' : 'about:')
+};
+
+export const WILDCARD = '*';
+
+export const WINDOW_TYPE = {
+    IFRAME: ('iframe' : 'iframe'),
+    POPUP:  ('popup' : 'popup')
+};

lib/index.js.flow

@@ -0,0 +1,5 @@
+/* @flow */
+
+export * from './utils';
+export * from './types';
+export * from './constants';

lib/types.js.flow

@@ -0,0 +1,40 @@
+/* @flow */
+
+// export something to force webpack to see this as an ES module
+export const TYPES = true;
+
+export type CrossDomainLocationType = {|
+
+|};
+
+export type CrossDomainWindowType = {|
+    location : string | CrossDomainLocationType,
+    self : CrossDomainWindowType,
+    closed : boolean,
+    open : (string, string, string) => CrossDomainWindowType,
+    close : () => void,
+    focus : () => void,
+    top : CrossDomainWindowType,
+    frames : $ReadOnlyArray<CrossDomainWindowType>,
+    opener ? : CrossDomainWindowType,
+    parent : CrossDomainWindowType,
+    length : number,
+    postMessage : (string, string) => void
+|};
+
+export type SameDomainWindowType = Object & {|
+    location : string | Object,
+    self : CrossDomainWindowType,
+    closed : boolean,
+    open : (string, string, string) => CrossDomainWindowType,
+    close : () => void,
+    focus : () => void,
+    XMLHttpRequest : typeof XMLHttpRequest,
+    document : Document,
+    navigator : {|
+        userAgent : string,
+        mockUserAgent? : string
+    |}
+|};
+
+export type DomainMatcher = string | $ReadOnlyArray<string> | $ReadOnlyArray<string> | RegExp;

lib/util.js.flow

@@ -0,0 +1,11 @@
+/* @flow */
+
+export function isRegex(item : mixed) : boolean {
+    // $FlowFixMe method-unbinding
+    return Object.prototype.toString.call(item) === '[object RegExp]';
+}
+
+// eslint-disable-next-line no-unused-vars
+export function noop(...args : $ReadOnlyArray<mixed>) {
+    // pass
+}