README: Just point to Wiki for build instructions

Getting started

---------------

To get started with Android/LineageOS, you'll need to get

familiar with [Repo](https://source.android.com/source/using-repo.html) and [Version Control with Git](https://source.android.com/source/version-control.html).

To initialize your local repository using the LineageOS trees, use a command like this:

```

repo init -u git://github.com/LineageOS/android.git -b lineage-18.0

```

Then to sync up:

```

repo sync

```

Please see the [LineageOS Wiki](https://wiki.lineageos.org/) for building instructions, by device.