Add minor improvements to the docs

docs/tutorials/learn.md

@@ -357,7 +357,7 @@ even : Nat -> Bool;
 even :=
   let
     even' : Nat -> Bool;
-    odd': Nat -> Bool;
+    odd' : Nat -> Bool;
 
     even' zero := true;
     even' (suc n) := odd' n;
@@ -725,7 +725,7 @@ type Maybe (A : Type) :=
 For example, one could define the tail function as:
 
 ```juvix
-tail' : {A : Type} -> List A -> Maybe A
+tail' : {A : Type} -> List A -> Maybe (List A)
 tail' (_ :: xs) := just xs;
 tail' nil := nothing;
 ```

docs/tutorials/vscode.md

@@ -1,6 +1,6 @@
 # Juvix VSCode extension tutorial
 
-To install the Juvix VSCode extension, click on the "Extensions" button
+To install the [Juvix VSCode extension][vscode-marketplace], click on the "Extensions" button
 in the left panel and search for the "Juvix" extension by Heliax.
 
 Once you've installed the Juvix extension, you can open a Juvix file.
@@ -36,3 +36,5 @@ The functions of the buttons are as follows.
   the executable run is displayed in a separate window.
 - Html preview. Generates HTML documentation for the current file and
   displays it in a separate window.
+
+[vscode-marketplace]: https://marketplace.visualstudio.com/items?itemName=heliax.juvix-mode