PR feedback: add installation instructions

DEVELOPMENT.md

@@ -6,6 +6,16 @@ This document outlines development practices that we follow while developing thi
 
 The included demo app utilizes a [sandbox sample merchant server](https://braintree-sample-merchant.herokuapp.com) hosted on Heroku.
 
+## SwiftLint
+
+Ensure that you have [SwiftLint](https://github.com/realm/SwiftLint) installed as we utilize it within our project.
+
+To install via [Homebrew](https://brew.sh/) run:
+```
+brew install swiftlint
+```
+Our Xcode workspace has a `Run Phase` which integrates in `SwiftLint` so the only prerequisite is installing via `Homebrew`.
+
 ## Tests
 
 Each module has a corresponding unit test target. These can be run individually, or all at once via the `UnitTests` scheme.

README.md

@@ -84,6 +84,9 @@ Versions 4.9.6 and below use outdated SSL certificates and are unsupported.
 
 ## Demo
 
+### Prerequisites
+Our Xcode project uses SwiftLint, see [DEVELOPMENT.md](https://github.com/braintree/braintree_ios/blob/main/DEVELOPMENT.md#swiftlint) for installation instructions
+
 1. Run `pod install`
     * There is a known M1 mac issue with CocoaPods. See [this solution](https://github.com/CocoaPods/CocoaPods/issues/10220#issuecomment-730963835) to resolve `ffi` dependency issues.
 2. Resolve the Swift Package Manager packages if needed: `File` > `Packages` > `Resolve Package Versions` or by running `swift package resolve` in Terminal