Upgrade tsconfig target to es6

[janeyx99]

Currently, when I try to upgrade with no changes, we get a ton of compilation errors when running yarn build:

node_modules/@types/babel__core/index.d.ts:13:20 - error TS2307: Cannot find module '@babel/types'.

13 import * as t from "@babel/types";
                      ~~~~~~~~~~~~~~

node_modules/@types/babel__core/index.d.ts:14:31 - error TS2307: Cannot find module '@babel/parser'.

14 import { ParserOptions } from "@babel/parser";
                                 ~~~~~~~~~~~~~~~

node_modules/@types/babel__generator/index.d.ts:9:20 - error TS2307: Cannot find module '@babel/types'.

9 import * as t from "@babel/types";
                     ~~~~~~~~~~~~~~

node_modules/@types/babel__template/index.d.ts:9:31 - error TS2307: Cannot find module '@babel/parser'.

9 import { ParserOptions } from "@babel/parser";
                                ~~~~~~~~~~~~~~~

node_modules/@types/babel__template/index.d.ts:10:54 - error TS2307: Cannot find module '@babel/types'.

10 import { Expression, File, Program, Statement } from "@babel/types";
                                                        ~~~~~~~~~~~~~~

node_modules/@types/babel__traverse/index.d.ts:10:20 - error TS2307: Cannot find module '@babel/types'.

10 import * as t from "@babel/types";
                      ~~~~~~~~~~~~~~

node_modules/@types/babel__traverse/index.d.ts:30:5 - error TS2411: Property 'scope' of type 'Scope' is not assignable to string index type '(VisitNodeFunction<S, any> & VisitNodeFunction<S, any>) | (VisitNodeFunction<S, any> & VisitNodeObject<S, any>) | (VisitNodeObject<...> & VisitNodeFunction<...>) | (VisitNodeObject<...> & VisitNodeObject<...>)'.

30     scope?: Scope;
       ~~~~~

node_modules/@types/babel__traverse/index.d.ts:31:5 - error TS2411: Property 'noScope' of type 'boolean' is not assignable to string index type '(VisitNodeFunction<S, any> & VisitNodeFunction<S, any>) | (VisitNodeFunction<S, any> & VisitNodeObject<S, any>) | (VisitNodeObject<...> & VisitNodeFunction<...>) | (VisitNodeObject<...> & VisitNodeObject<...>)'.

31     noScope?: boolean;
       ~~~~~~~

node_modules/@types/jest/index.d.ts:477:51 - error TS2307: Cannot find module 'jest-diff'.

477             diff(a: any, b: any, options?: import("jest-diff").DiffOptions): string | null;
                                                      ~~~~~~~~~~~

node_modules/@types/source-map-support/index.d.ts:9:30 - error TS2307: Cannot find module 'source-map'.

9 import { RawSourceMap } from 'source-map';
                               ~~~~~~~~~~~~

src/action.ts:2:19 - error TS2307: Cannot find module 'probot-actions-adapter'.

2 import adapt from 'probot-actions-adapter';
                    ~~~~~~~~~~~~~~~~~~~~~~~~

src/auto-cc-bot.ts:3:25 - error TS2307: Cannot find module 'probot'.

3 import * as probot from 'probot';
                          ~~~~~~~~

src/auto-label-bot.ts:2:25 - error TS2307: Cannot find module 'probot'.

2 import * as probot from 'probot';
                          ~~~~~~~~

src/ciflow-bot.ts:1:25 - error TS2307: Cannot find module 'probot'.

1 import * as probot from 'probot';
                          ~~~~~~~~

src/handler.ts:1:26 - error TS2307: Cannot find module '@probot/serverless-lambda'.

1 import {serverless} from '@probot/serverless-lambda';
                           ~~~~~~~~~~~~~~~~~~~~~~~~~~~

src/handler.ts:3:19 - error TS2307: Cannot find module './'.

3 import appFn from './';
                    ~~~~

src/index.ts:7:27 - error TS2307: Cannot find module 'probot'.

7 import {Application} from 'probot';
                            ~~~~~~~~

src/index.ts:23:1 - error TS1203: Export assignment cannot be used when targeting ECMAScript modules. Consider using 'export default' or another module format instead.

23 export = runBot;
   ~~~~~~~~~~~~~~~~

src/trigger-circleci-workflows.ts:1:19 - error TS2307: Cannot find module 'axios'.

1 import axios from 'axios';
                    ~~~~~~~

src/trigger-circleci-workflows.ts:2:25 - error TS2307: Cannot find module 'probot'.

2 import * as probot from 'probot';
                          ~~~~~~~~

src/utils.ts:1:25 - error TS2307: Cannot find module 'probot'.

1 import * as probot from 'probot';
                          ~~~~~~~~

Found 21 errors.