Add Bech32 decodeNpub, decodeNsec, decodeNote, decodeNprofile…

…, `decodeNevent` and `decodeNrelay` methods (#23)

Nostra/Bech32.fs

@@ -236,4 +236,40 @@ module Shareable =
                     Some (NRelay(Encoding.ASCII.GetString (List.toArray relayUrl)))
                 | _ -> None                
             | _ -> None
-            )
+            )
+
+    let decodeNpub str =
+        decode str
+        |> Option.bind (function
+            | NPub pk -> Some (XOnlyPubKey pk)
+            | _ ->  None)
+
+    let decodeNsec str =
+        decode str
+        |> Option.bind (function
+            | NSec sk -> Some sk
+            | _ ->  None)
+
+    let decodeNote str =
+        decode str
+        |> Option.bind (function
+            | Note eventId -> Some eventId
+            | _ ->  None)
+
+    let decodeNprofile str =
+        decode str
+        |> Option.bind (function
+            | NProfile (pk, relays) -> Some (pk, relays)
+            | _ ->  None)
+
+    let decodeNevent str =
+        decode str
+        |> Option.bind (function
+            | NEvent (eventId, relays, author, kind) -> Some (eventId, relays, author, kind)
+            | _ ->  None)
+
+    let decodeNrelay str =
+        decode str
+        |> Option.bind (function
+            | NRelay relays -> Some relays
+            | _ ->  None)