Add Single file archive method.

types/enviornment.d.ts

@@ -46,6 +46,10 @@ declare global {
       PDF_MARGIN_TOP?: string;
       PDF_MARGIN_BOTTOM?: string;
 
+      // PDF archive settings
+      SINGLEFILE_ARCHIVE_COMMAND?: string;
+      SINGLEFILE_ARCHIVE_HTTP_API?: string;
+
       //
       // SSO Providers
       //

types/global.ts

@@ -128,12 +128,14 @@ export enum ArchivedFormat {
   jpeg,
   pdf,
   readability,
+  singlefile,
 }
 
 export enum LinkType {
   url,
   pdf,
   image,
+  singlefile,
 }
 
 export enum TokenExpiry {