README.adoc: fix and improve Go instructions

It is recognised by shared-mime-info.

README.adoc

@@ -36,12 +36,25 @@ Runtime dependencies: libcrypto (OpenSSL 1.1 API)
 In addition to the C++ version, also included is a native Go port,
 which has enhanced PDF 1.5 support:
 
- $ go get janouch.name/pdf-simple-sign/cmd/pdf-simple-sign
+----
+$ go install janouch.name/pdf-simple-sign/cmd/pdf-simple-sign@master
+----
 
-And a crude external VFS for Midnight Commander, that may be used to extract
+and a crude external VFS for Midnight Commander, that may be used to extract
 all streams from a given PDF file:
 
- $ go get janouch.name/pdf-simple-sign/cmd/extfs-pdf
+----
+$ GOBIN=$HOME/.local/share/mc/extfs.d \
+  go install janouch.name/pdf-simple-sign/cmd/extfs-pdf@master
+----
+
+To enable the VFS, edit your _~/.config/mc/mc.ext.ini_ to contain:
+
+----
+[pdf]
+Type=^PDF
+Open=%cd %p/pdf://
+----
 
 Contributing and Support
 ------------------------

cmd/extfs-pdf/main.go

@@ -1,5 +1,5 @@
 //
-// Copyright (c) 2021, Přemysl Eric Janouch <p@janouch.name>
+// Copyright (c) 2021 - 2024, Přemysl Eric Janouch <p@janouch.name>
 //
 // Permission to use, copy, modify, and/or distribute this software for any
 // purpose with or without fee is hereby granted.
@@ -46,6 +46,8 @@ func streamSuffix(o *pdf.Object) string {
 			return "jp2"
 		case "DCTDecode":
 			return "jpg"
+		case "FlateDecode":
+			return "zz"
 		default:
 			return filter.String
 		}