Add middleware documentation

Author: nandi95

docs/middlewares.md

@@ -1,2 +1,11 @@
 # Middlewares
 
+Middlewares are an optional bit of logic to transform the given data at various lifecycle points.
+
+### Path
+
+To add a path middleware create a class that implements `\Vyuldashev\LaravelOpenApi\Contracts\PathMiddleware` then register it by referencing it in the  `openapi.collections.default.middlewares.paths` config array like `MyPathMiddleware::class`
+
+Available lifecycle points are:
+ - `before` - after collecting all `RouteInformation` but before processing them.
+ - `after` - after the `PathItem` has been built.