docs: Update Unleash architecture diagram (#1549)

* docs: Update Unleash architecture digram

* fix: typo an -> a

* docs(fix): fix img link in readme

* docs: update architecture graph

README.md

@@ -162,7 +162,7 @@ If you're looking for one of the following features, please take a look at our [
 
 ## Architecture
 
-<img src="./.github/Unleash_architecture.svg" title="Unleash System Overview" />
+<img src="./website/static/img/unleash-architecture.svg" title="Unleash System Overview" />
 
 Read more in the [*system overview* section of the Unleash documentation](https://docs.getunleash.io/user_guide/unleash_overview#system-overview).
 

website/docs/user_guide/unleash_overview.md

@@ -20,7 +20,7 @@ Before you can connect your application to Unleash you need a Unleash server. Yo
 
 ### System Overview {#system-overview}
 
-![system_overview](/img/Unleash_architecture.svg 'System Overview')
+![A visual overview of an Unleash system as described in the following paragraph.](/img/unleash-architecture.svg 'System Overview')
 
 - **Unleash API** - The service holding all feature toggles and their configurations. Configurations declare which activation strategies to use and which parameters they should get. [API documentation](/api)
 - **Unleash Admin UI** - The dashboard used to manage feature toggles, define new strategies, look at metrics, etc. [Create your first feature toggle](user_guide/create-feature-toggle.md)