Add README.md and CHANGELOG.md

Fix typo in UPGRADING.md

Author: ericproulx

CHANGELOG.md

@@ -11,6 +11,7 @@
 * [#2549](https://github.com/ruby-grape/grape/pull/2549): Delegate cookies management to `Grape::Request` - [@ericproulx](https://github.com/ericproulx).
 * [#2554](https://github.com/ruby-grape/grape/pull/2554): Remove `Grape::Http::Headers` and `Grape::Util::Lazy::Object` - [@ericproulx](https://github.com/ericproulx).
 * [#2556](https://github.com/ruby-grape/grape/pull/2556): Remove unused `Grape::Request::DEFAULT_PARAMS_BUILDER` constant - [@eriklovmo](https://github.com/eriklovmo).
+* [#2557](https://github.com/ruby-grape/grape/pull/2557): Add lint! - [@ericproulx](https://github.com/ericproulx).
 * Your contribution here.
 
 #### Fixes

README.md

@@ -28,6 +28,8 @@
     - [Header](#header)
     - [Accept-Version Header](#accept-version-header)
     - [Param](#param)
+- [Linting](#linting)
+  - [Bug with Rack::ETag under Rack 3.X](#bug-in-racketag-under-rack-3x)
 - [Describing Methods](#describing-methods)
 - [Configuration](#configuration)
 - [Parameters](#parameters)
@@ -650,6 +652,25 @@ version 'v1', using: :param, parameter: 'v'
     curl http://localhost:9292/statuses/public_timeline?v=v1
 
 
+## Linting
+
+You can check if your API is in conformance with [Rack's specification](https://github.com/rack/rack/blob/main/SPEC.rdoc) by calling `lint!` at the API level or through [configuration](#configuration):
+```ruby
+# API Level
+class Api < Grape::API
+  lint!
+end
+# OR through configuration
+Grape.configure do |config|
+  config.lint = true
+end
+# OR
+Grape.config.lint = true
+```
+
+### Bug in Rack::ETag under Rack 3.X
+If you're using Rack 3.X and the `Rack::Etag` middleware (used by [Rails](https://guides.rubyonrails.org/rails_on_rack.html#inspecting-middleware-stack)), a [bug](https://github.com/rack/rack/pull/2324) related to linting has been fixed in [3.1.13](https://github.com/rack/rack/blob/v3.1.13/CHANGELOG.md#3113---2025-04-13) and [3.0.15](https://github.com/rack/rack/blob/v3.1.13/CHANGELOG.md#3015---2025-04-13) respectively.
+
 ## Describing Methods
 
 You can add a description to API methods and namespaces. The description would be used by [grape-swagger][grape-swagger] to generate swagger compliant documentation.

UPGRADING.md

@@ -130,7 +130,7 @@ When using together with `Grape::Extensions::Hash::ParamBuilder`, `route_param`
 This was a regression introduced by [#2326](https://github.com/ruby-grape/grape/pull/2326) in Grape v1.8.0.
 
 ```ruby
-grape.configure do |config|
+Grape.configure do |config|
   config.param_builder = Grape::Extensions::Hash::ParamBuilder
 end