Update SwiftLint to 0.39.2 (#295)

* Update SwiftLint to 0.39.2

* Enable a bunch of extra rules

* Fix all warnings

* Ignore this Xcode generated folder

Co-authored-by: Olivier Halligon <olivier@halligon.net>

Sources/Errors.swift

@@ -55,7 +55,6 @@ public protocol ErrorReporter: AnyObject {
 }
 
 open class SimpleErrorReporter: ErrorReporter {
-
   open func renderError(_ error: Error) -> String {
     guard let templateError = error as? TemplateSyntaxError else { return error.localizedDescription }
 
@@ -74,10 +73,9 @@ open class SimpleErrorReporter: ErrorReporter {
         """
     }
 
-    var descriptions = templateError.stackTrace.reduce([]) { $0 + [describe(token: $1)] }
+	var descriptions = templateError.stackTrace.reduce(into: []) { $0.append(describe(token: $1)) }
     let description = templateError.token.map(describe(token:)) ?? templateError.reason
     descriptions.append(description)
     return descriptions.joined(separator: "\n")
   }
-
 }