Add more data to availableDownloads

lib/GHCup.hs

@@ -51,6 +51,18 @@ availableDownloads = Map.fromList
                     )
                   ]
                 )
+              , ( Linux Debian
+                , Map.fromList
+                  [ ( Nothing
+                    , mkGHCUrl
+                      "~ghc/8.6.5/ghc-8.6.5-x86_64-debian9-linux.tar.xz"
+                    )
+                  , ( Just $ (\(Right x) -> x) $ versioning (fS "8")
+                    , mkGHCUrl
+                      "~ghc/8.6.5/ghc-8.6.5-x86_64-debian8-linux.tar.xz"
+                    )
+                  ]
+                )
               ]
             )
           ]