changes made to add TWRP for OnePlus 6

## Temporarily booting a custom recovery using `fastboot`

1. Download a custom recovery - you can download [TWRP](https://dl.twrp.me/{{ custom_recovery_codename }}).

{% if device.alternate_twrp %}

> An [alternate location]({{ device.alternate_twrp }}) to download TWRP

{% endif %}

{% if device.twrp_version %}

  > The version of TWRP we used to test the ROM was {{ device.twrp_version }}

{% endif %}

1. Connect your device to your PC via USB.

1. On the computer, open a command prompt (on Windows) or terminal (on Linux or macOS) window, and type:

    ```