add local TailwindCSS, fix side bar folder view, add more function to Markdown editor and allow .markdown files

internal/models/models.go

@@ -45,7 +45,7 @@ type ImageStorageInfo struct {
 func GetFileType(extension string, allowedImageExts, allowedFileExts []string) FileType {
 	ext := strings.ToLower(strings.TrimPrefix(extension, "."))
 
-	if ext == "md" {
+	if ext == "md" || ext == "markdown" {
 		return FileTypeMarkdown
 	}