Map `.manifest` → `text/cache-manifest` media type

The specification for the manifest file for web applications was
recently updated¹ and it changed one of the recommended file extensions
from `.manifest` to the unique `.webmanifest`².

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

¹ 0eecadd090
² https://github.com/w3c/manifest/issues/346

CHANGELOG.md

@@ -1,5 +1,6 @@
 ### HEAD
 
+* Map the `.manifest` file extension to the `text/cache-manifest` media type.
 * Update the list of resources to be compressed
   ([d7e0e1b](https://github.com/h5bp/server-configs-nginx/commit/d7e0e1b)).
 * Update `mime.types`

mime.types

@@ -19,6 +19,7 @@ types {
 
   # Manifest files
 
+    application/manifest+json             webmanifest;
     application/x-web-app-manifest+json   webapp;
     text/cache-manifest                   appcache;