doc/tutorial: fix typos

Closes #47
https://github.com/cuelang/cue/pull/47

GitOrigin-RevId: eb0f57b30701026d0e034c56afd7453cd28f61d3
Change-Id: I3498873e6d17a1609290bae7f98ef08a38ce1b67
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/2100
Reviewed-by: Marcel van Lohuizen <mpvl@google.com>
diff --git a/doc/tutorial/basics/aliases.md b/doc/tutorial/basics/aliases.md
index 66f5b71..11959a4 100644
--- a/doc/tutorial/basics/aliases.md
+++ b/doc/tutorial/basics/aliases.md
@@ -8,7 +8,7 @@
 
 A typical use case is to provide access to a shadowed field.
 
-Alias are not members of a struct. They can be referred to only within the
+Aliases are not members of a struct. They can be referred to only within the
 struct, and they do not appear in the output.
 
 <!-- CUE editor -->
diff --git a/doc/tutorial/basics/sumstruct.md b/doc/tutorial/basics/sumstruct.md
index 25e76a4..319c162 100644
--- a/doc/tutorial/basics/sumstruct.md
+++ b/doc/tutorial/basics/sumstruct.md
@@ -4,7 +4,7 @@
 
 # Disjunctions of Structs
 
-Disjunction work for any type.
+Disjunctions work for any type.
 
 In this example we see that a `floor` of some specific house
 has an exit on level 0 and 1, but not on any other floor.