Add full README

Author: erwinvaneyk

README.md

@@ -1 +1,33 @@
-# CA Completer
+# Cert Completer
+
+Cert Completer is a small Kubernetes operator that ensures that all TLS secrets 
+have a valid `ca.crt`.
+
+It addresses a specific issue with the (Let's Encrypt) ACME provider in 
+[cert-manager](https://github.com/jetstack/cert-manager), where certificates 
+are lacking a CA in the `ca.crt` key of the generated secret. Although issues 
+have been raised to fill the `ca.crt` 
+(see [#2111](https://github.com/jetstack/cert-manager/issues/2111) and 
+[#1571](https://github.com/jetstack/cert-manager/issues/1571)), it is not clear 
+if and when these issues will be resolved. Cert Completer is an attempt to patch 
+this issue immediately regardless of the cert-manager version.
+
+To provide each TLS secret with a `ca.crt`, the operator parses the certificate 
+chain in `tls.crt`. It uses the last (top-most) certificate in this chain for 
+`ca.crt`. Although this does not guarantee that `ca.crt` contains a root CA, it 
+does guarantee that the CA present is valid for the TLS secret. 
+
+## Installation
+
+Using pre-built resources:
+```bash
+kubectl apply -f https://raw.githubusercontent.com/erwinvaneyk/cert-completer/master/cert-completer.yaml
+```
+
+Using Kustomize (requires kubectl > 1.15):
+```bash
+kubectl apply -k github.com/erwinvaneyk/cert-completer//config/default
+```
+
+Clone and modify [./config/default/kustomization.yaml] for alternative, 
+custom deployments.