added support for multilingual 404 page redirects

exampleSite/config/development/server.toml

@@ -0,0 +1,13 @@
+# defaultContentLanguageInSubdir must be true for this to work.
+
+# Other languages redirects
+# [[redirects]]
+# from = '/fr/**'
+# to = '/fr/404.html'
+# status = 404
+
+# Default language must be last.
+[[redirects]]
+from = '/**'
+to = '/en/404.html'
+status = 404