added description header field

docs/reference/createPlugin-feature-flags.md

@@ -1,6 +1,7 @@
 ---
 id: createPlugin-feature-flags
 title: createPlugin - feature flags
+description: Documentation on createPlugin - feature flags
 ---
 
 The `featureFlags` object passed to the `register` function makes it possible

docs/reference/createPlugin-router.md

@@ -1,6 +1,7 @@
 ---
 id: createPlugin-router
 title: createPlugin - router
+description: Documentation on createPlugin - router
 ---
 
 The router that is passed to the `register` function makes it possible for

docs/reference/createPlugin.md

@@ -1,6 +1,7 @@
 ---
 id: createPlugin
 title: createPlugin
+description: Documentation on createPlugin
 ---
 
 Taking a plugin config as argument and returns a new plugin.