fix rendering templates created from string literals

Sources/Environment.swift

@@ -43,6 +43,8 @@ public struct Environment {
   }
   
   func render(template: Template, context: [String: Any]?) throws -> String {
+    // update temaplte environment as it cen be created from string literal with default environment
+    template.environment = self
     errorReporter.context = ErrorReporterContext(template: template)
     do {
       return try template.render(context)

Sources/Template.swift

@@ -8,7 +8,7 @@ let NSFileNoSuchFileError = 4
 /// A class representing a template
 open class Template: ExpressibleByStringLiteral {
   let templateString: String
-  let environment: Environment
+  internal(set) var environment: Environment
   let tokens: [Token]
 
   /// The name of the loaded Template if the Template was loaded from a Loader