docs: add link to mail list archive

Signed-off-by: Sami Kerola <kerolasa@iki.fi>

README

@@ -7,8 +7,9 @@
 
 MAILING LIST:
 
-      E-MAIL: util-linux@vger.kernel.org
-      URL:    http://vger.kernel.org/vger-lists.html#util-linux
+      E-MAIL:  util-linux@vger.kernel.org
+      URL:     http://vger.kernel.org/vger-lists.html#util-linux
+      ARCHIVE: https://lore.kernel.org/util-linux/
 
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        - more than 100K characters