Update docs

README.md

@@ -1,3 +1,44 @@
-# silverstripe-cdnrewrite
+# Silverstripe CDN Rewrite
 
+Provides a simple method of rewriting the URLs of assets and resources to allow the use of a subdomain or external CDN service
 
+
+# Requirements
+*Silverstripe 4.x
+
+# Installation
+* Install the code with `composer require dorsetdigital/silverstripe-cdnrewrite`
+* Run a `dev/build?flush` to update your project
+
+# Usage
+
+The module won't make any changes to your site unless you do a bit of configuration.  There are a few options to set, done in a yml file:
+
+
+```yaml
+---
+Name: cdnconfig
+---
+
+DorsetDigital\CDNRewrite\CDNMiddleware:
+  cdn_rewrite: true
+  cdn_domain: 'https://cdn.example.com'
+  rewrite_assets: true
+  rewrite_resources: true
+  add_debug_headers: true
+  enable_in_dev: true
+```
+
+The options are hopefully fairly self explanatory:
+
+* `cdn_rewrite` - globally enables and disables the module (default false - disabled)
+* `cdn_domain` - the full domain name of the CDN (required to enable module)
+* `rewrite_assets` - whether to rewrite references to the 'assets' directory (default false)
+* `rewrite_resources` - whether to rewrite references to the 'resources' directory (default false)
+* `add_debug_headers` - if enabled, adds extra HTML headers to show the various operations being applied (default false)
+* `enable_in_dev` - enable the CDN in dev mode (default false)
+
+
+# Credits
+* Very much inspired by [Werner Krauss' silverstripe-cdnrewrite](https://github.com/wernerkrauss/silverstripe-cdnrewrite)
+* As always, thanks to the core team for all their hard work.