Added "lenient" feature

Cargo.toml

@@ -16,4 +16,5 @@ chrono = { version = "0.4", default-features = false, features = [ "std" ] }
 [features]
 default = ["parser"]
 parser = ["nom"]
+lenient = []
 

src/playlist.rs

@@ -468,6 +468,7 @@ impl AlternativeMedia {
         let default = is_yes!(attrs, "DEFAULT");
         let autoselect = is_yes!(attrs, "AUTOSELECT");
 
+        #[cfg(feature = "lenient")]
         if media_type != AlternativeMediaType::Subtitles && attrs.contains_key("FORCED") {
             return Err(String::from(
                 "FORCED attribute must not be included in non-SUBTITLE Alternative Medias",