[installer]: create readme

Author: Simon Emms

installer/README.md

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+# Installer
+
+The best way to get started with Gitpod self-hosted
+
+> This guide assumes that a compatible infrastructure is in place. Please
+> refer to the [Gitpod docs](https://www.gitpod.io/docs/self-hosted/latest/installation)
+> for instructions on how to create the infrastructure.
+
+# Key Concepts
+
+The Installer is a complete replacement for our Helm charts. Over time,
+this had grown to be too complex to effectively support and was a barrier
+to entry for new users - the base config was many hundreds of lines long
+and did not have effective validation on it. By contrast, the Installer's
+config is < 50 lines long and can be fully validated before running.
+
+Conceptually, the process is now:
+1. generate a base config
+2. amend the config for your own use-case
+3. validate
+4. render the Kubernetes YAML
+5. `kubectl apply`
+
+# Quickstart
+
+## Create a gitpod-installer script
+
+```shell
+#!/bin/bash
+
+VERSION="${VERSION:-main.1844}"
+
+docker run -it --rm \
+  -v $PWD:/gitpod \
+  -v $HOME/.kube:/root/.kube \
+  eu.gcr.io/gitpod-core-dev/build/installer:${VERSION} \
+  $@
+```
+
+Save this in your `$PATH` as `gitpod-installer` and make executable
+
+## Generate the base config
+
+```shell
+gitpod-installer init > config.yaml
+```
+
+## Validate
+
+```shell
+# Checks the validity of the configuration YAML
+gitpod-installer validate config --config /gitpod/config.yaml
+
+# Checks that your cluster is ready to install Gitpod
+gitpod-installer validate cluster --kubeconfig /root/.kube/config --config /gitpod/config.yaml
+```
+
+Any errors here must be fixed before deploying. See [Cluster Dependencies](#cluster-dependencies)
+and [Config](#config) for more details.
+
+## Render the YAML
+
+```shell
+gitpod-installer render --config /gitpod/config.yaml > gitpod.yaml
+```
+
+## Deploy
+
+```shell
+kubectl apply -f gitpod.yaml
+```
+
+# Cluster Dependencies
+
+# Config
+
+# Todo
+
+PRs/comments welcome
+
+- [ ] [Improve distribution of gitpod-installer binaries](https://github.com/gitpod-io/gitpod/issues/6766)