Bearer token Authorization support

[parallels999]

Closes #352
Tested, this PR does not affect current functionality, also works with third party jwt tokens

When making requests using API tokens, the token should be included in the Authorization header as a Bearer token.
When the mobile application uses the token to make an API request to your application, it should pass the token in the Authorization header as a Bearer token. "Laravel Sanctum"

Broadcast::routes(["middleware" => ['auth:api',/*'auth:sanctum',*/]]);

Current:

var TOKEN='*******';
{
  // csrfToken: '******'
  auth: {
      headers: {
          Authorization: "Bearer " + TOKEN
      },
  },
  userAuthentication: {
      headers: {
          Authorization: "Bearer " + TOKEN
      },
  },
}

New(Shorter):

{
  // csrfToken: '******'
  bearerToken: '*******',
}

Sources:
https://laravel.com/docs/9.x/sanctum#issuing-api-tokens
PR: [9.x] User authentication for Pusher framework#42531
signin() method: https://pusher.com/docs/channels/using_channels/user-authentication/#sign-in
#189 (comment)
#26 (comment)
#26 (comment)
#26 (comment)
#26 (comment)
#282 (comment)
#219 (comment)

> npm run compile && npm run declarations
> laravel-echo@1.[13](https://github.com/laravel/echo/runs/8038132230?check_suite_focus=true#step:6:14).1 compile
> ./node_modules/.bin/rollup -c
./src/echo.ts → ./dist/echo.js, ./dist/echo.common.js...
(!) Mixing named and default exports
https://rollupjs.org/guide/en/#outputexports
The following entry modules are using named and default exports together:
src/echo.ts

Consumers of your bundle will have to use chunk['default'] to access their default export, which may not be what you want. Use `output.exports: 'named'` to disable this warning
created ./dist/echo.js, ./dist/echo.common.js in 4.5s