docs: Fix docs links in plugin readmes

packages/admin-ui-plugin/README.md

@@ -2,4 +2,4 @@
 
 `npm install @vendure/admin-ui-plugin`
 
-For documentation, see [www.vendure.io/docs/plugins/admin-ui-plugin](www.vendure.io/docs/plugins/admin-ui-plugin)
+For documentation, see [www.vendure.io/docs/plugins/admin-ui-plugin](https://www.vendure.io/docs/plugins/admin-ui-plugin)

packages/asset-server-plugin/README.md

@@ -4,4 +4,4 @@ The `AssetServerPlugin` serves assets (images and other files) from the local fi
 
 `npm install @vendure/asset-server-plugin`
 
-For documentation, see [www.vendure.io/docs/plugins/asset-server-plugin](www.vendure.io/docs/plugins/asset-server-plugin)
+For documentation, see [www.vendure.io/docs/plugins/asset-server-plugin](https://www.vendure.io/docs/plugins/asset-server-plugin)

packages/elasticsearch-plugin/README.md

@@ -4,6 +4,6 @@ The `ElasticsearchPlugin` uses Elasticsearch to power the the Vendure product se
 
 `npm install @vendure/elasticsearch-plugin`
 
-~~For documentation, see [www.vendure.io/docs/plugins/elasticsearch-plugin](www.vendure.io/docs/plugins/elasticsearch-plugin)~~
+For documentation, see [www.vendure.io/docs/plugins/elasticsearch-plugin](https://www.vendure.io/docs/plugins/elasticsearch-plugin)
 
 Status: work in progress

packages/email-plugin/README.md

@@ -4,4 +4,4 @@ The `EmailPlugin` generates and sends emails based on Vendure server events.
 
 `npm install @vendure/email-plugin`
 
-For documentation, see [www.vendure.io/docs/plugins/email-plugin](www.vendure.io/docs/plugins/email-plugin)
+For documentation, see [www.vendure.io/docs/plugins/email-plugin](https://www.vendure.io/docs/plugins/email-plugin)