Make `IntercomClient::$password` explicitly nullable (#373)

This prevents a deprecation warning from showing up since PHP 8.4

```
Deprecated: Intercom\IntercomClient::__construct(): Implicitly marking parameter $password as nullable is deprecated, the explicit nullable type must be used instead in /<redacted-path>/vendor/intercom/intercom-php/src/IntercomClient.php on line 148
```

Http: add support for PSR17/PSR18 and drop usage of deprecated client…

… discovery (#363)

Merge pull request #342 from intercom/jn/update-readme

update readme

Merge pull request #342 from intercom/jn/update-readme

update readme

Fix bug where handleResponse() is called twice (#318)

You'll probably want better tests here....

fixing broken Contacts update method (#311)

* fixing broken update method

"update" should follow the same pattern as other methods like deleteContact and getContact that require "id" based on the API documentation.

* updates tests and README for broken Contact method

Update readme with API versions (#308)

Add support for teams (#305)

* Add support for teams

* Typo fix

Add support for listing users of a company (Fixes: #285) (#287)

* Add support for listing users of a company

* Remove unneeded method and add to readme

* Remove unneeded test

Add .gitattributes to shrink installs (#286)