add more file formats to reactor

Fixes #1942
Fixes elm-lang/elm-reactor#190
Fixes elm-lang/elm-reactor#224
Fixes elm-lang/elm-reactor#228

Author: evancz

terminal/src/Develop.hs

@@ -218,6 +218,7 @@ mimeTypeDict =
     , ".m3u"     ==> "audio/x-mpegurl"
     , ".mov"     ==> "video/quicktime"
     , ".mp3"     ==> "audio/mpeg"
+    , ".mp4"     ==> "video/mp4"
     , ".mpeg"    ==> "video/mpeg"
     , ".mpg"     ==> "video/mpeg"
     , ".ogg"     ==> "application/ogg"
@@ -241,6 +242,8 @@ mimeTypeDict =
     , ".txt"     ==> "text/plain"
     , ".wav"     ==> "audio/x-wav"
     , ".wax"     ==> "audio/x-ms-wax"
+    , ".webm"    ==> "video/webm"
+    , ".webp"    ==> "image/webp"
     , ".wma"     ==> "audio/x-ms-wma"
     , ".wmv"     ==> "video/x-ms-wmv"
     , ".woff"    ==> "font/woff"