improve mime typing

Signed-off-by: kim (grufwub) <grufwub@gmail.com>

gemini/mime.go

@@ -2,6 +2,10 @@
 package gemini
 
 var mimeTypes = map[string]string{
+	// Empty extension gets the default
+	"": "application/octet-stream",
+
+	// BEGIN DEFINITIONS
 	"123":                      "application/vnd.lotus-1-2-3",
 	"3dml":                     "text/vnd.in3d.3dml",
 	"3ds":                      "image/x-3ds",
@@ -1114,4 +1118,5 @@ var mimeTypes = map[string]string{
 	"zir":                      "application/vnd.zul",
 	"zirz":                     "application/vnd.zul",
 	"zmm":                      "application/vnd.handheld-entertainment+xml",
+	// END DEFINITIONS
 }