✏️ Fix typos in README and comment

Author: Zeta611

README.md

@@ -61,7 +61,7 @@ Below are some examples using simplebnf.
 
 ![System F](./examples/system-f.svg)
 
-The example below uses a `(y: 0.6em,)` inset dictionary to specify larger vertical spacing between entries. This is useful if your rules user superscripts heavily.
+The example below uses a `(y: 0.6em,)` inset dictionary to specify larger vertical spacing between entries. This is useful if your rules use superscripts heavily.
 
 ```typst
 #let esc(e) = $\\ #h(0pt) #e$

simplebnf.typ

@@ -4,7 +4,7 @@
 ) = {
   let content = body.pos().intersperse((none,) * 5 * 2).flatten()
 
-  // This 'set' calls defines a default value for all inset
+  // This 'set' call defines a default value for all inset
   // dimensions, so that callers can use `inset: (y: 1em,)` and have
   // the `x` dimension implicitly set at 0.28em as intended.
   set grid(inset: 0.28em)