[bluebird-global] Amend .finally() and update docs for es5 target.

types/bluebird-global/index.d.ts

@@ -31,6 +31,22 @@
  *    in the runtime. Do this by either importing bluebird.js via a `<script />` tag in your html or
  *    via importing it in your js entry file AND assigning it to the global Promise symbol.
  *
+ * c) if you're `--target`ing "es5", then you'll need to include the "es2015.iterable" lib typings to
+ *    let the bluebird.d.ts compile (requirement for Map, Iterable & friends). This is only for the
+ *    compile-time, since bluebird doesn't require these es6 features to be present in the runtime.
+ *    To summarise: when targeting "es5", make sure you have the follwing "lib" config in your tsconfig.json:
+ *
+ *    {
+ *      "compilerOptions": {
+ *        "lib": [
+ *          "es5",
+ *          "es2015.iterable",
+ *          "dom"
+ *          (more, if you need...)
+ *        ],
+ *      }
+ *    }
+ *
  * 3. Why so much effort?
  *
  * If a promise-polyfilling library wants to play nicely with TypeScript, it needs to augment
@@ -38,7 +54,7 @@
  * For various reasons this couldn't be done in The `bluebird` typings.
  *
  * 4. Contributors: After changing this file please manually test these cases (via altering ./tsconfig.json ):
- *   a. target es5, no `lib` key
+ *   a. target es5, with the following `lib` keys: "es5", "es2015.iterable", "dom"
  *   b. target es6, no `lib` key
  *   c. target es5, latest "es20xx", e.g. "es2017"
  *   d. target es6, latest "es20xx", e.g. "es2017"
@@ -128,7 +144,7 @@ declare global {
         /*
          * See comments above `then` for the reason why this is needed. Taken from esnext.promise.d.ts.
          */
-        finally(onfinally?: (() => void) | undefined | null): Bluebird<T>;
+        finally(onfinally?: (() => void) | undefined | null): Promise<T>;
     }
 
     /*

types/bluebird-global/tsconfig.json

@@ -2,7 +2,7 @@
     "compilerOptions": {
         "module": "commonjs",
         "lib": [
-            "es2017",
+            "es2018",
             "dom"
         ],
         "noImplicitAny": true,