fix(salsa.md): add punctuation to prevent confusion

src/salsa.md

@@ -148,9 +148,9 @@ this one depends on by specifying them as supertraits, as seen in the following
 example:
 
 ```rust,ignore
-/// This query group is going to contain queries that depend on derived values a
+/// This query group is going to contain queries that depend on derived values. A
 /// query group can access another query group's queries by specifying the
-/// dependency as a super trait query groups can be stacked as much as needed using
+/// dependency as a super trait. Query groups can be stacked as much as needed using
 /// that pattern.
 #[salsa::query_group(ParserStorage)]
 pub trait Parser: Inputs {