Rename package to swift-mustache (#27)

* Rename package to swift-mustache

* Update CI

Sources/Mustache/Lambda.swift

@@ -0,0 +1,50 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Hummingbird server framework project
+//
+// Copyright (c) 2021-2021 the Hummingbird authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See hummingbird/CONTRIBUTORS.txt for the list of Hummingbird authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+/// Lambda function. Can add this to object being rendered to filter contents of objects.
+///
+/// See http://mustache.github.io/mustache.5.html for more details on
+/// mustache lambdas. Lambdas work slightly differently in HummingbirdMustache though
+/// as they are passed a template representing the contained text and not the raw text
+/// e.g
+/// ```
+/// struct Object {
+///     let name: String
+///     let wrapped: MustacheLambda
+/// }
+/// let willy = Object(name: "Willy", wrapped: .init({ object, template in
+///     return "<b>\(template.render(object))</b>"
+/// }))
+/// let mustache = "{{#wrapped}}{{name}} is awesome.{{/wrapped}}"
+/// let template = try MustacheTemplate(string: mustache)
+/// let output = template.render(willy)
+/// print(output) // <b>Willy is awesome</b>
+/// ```
+///
+public struct MustacheLambda {
+    /// lambda callback
+    public typealias Callback = (Any, MustacheTemplate) -> String
+
+    let callback: Callback
+
+    /// Initialize `MustacheLambda`
+    /// - Parameter cb: function to be called by lambda
+    public init(_ cb: @escaping Callback) {
+        self.callback = cb
+    }
+
+    internal func run(_ object: Any, _ template: MustacheTemplate) -> String {
+        return self.callback(object, template)
+    }
+}