feat: kepub conversions

Working *.epub to *.kepub.epub file conversions when
using a Kobo reader. Updated docker file to include
`kepubify` to convert to kepub. If not available the
file is just sent without conversion.

server.go

@@ -1,12 +1,15 @@
 package main
 
 import (
+	"fmt"
 	"net/http"
 	"os"
 
 	"github.com/evan-buss/kobo-opds-proxy/html"
 )
 
+type Middleware func(http.HandlerFunc) http.HandlerFunc
+
 type Server struct {
 	addr   string
 	router *http.ServeMux
@@ -18,9 +21,11 @@ func NewServer() *Server {
 		port = "8080"
 	}
 
+	fmt.Println(os.Getenv("PATH"))
+
 	router := http.NewServeMux()
 	router.HandleFunc("GET /{$}", handleHome())
-	router.HandleFunc("GET /feed", handleFeed())
+	router.HandleFunc("GET /feed", handleFeed("tmp/"))
 	router.Handle("GET /static/", http.FileServer(http.FS(html.StaticFiles())))
 
 	return &Server{