docs: fix typos (#18866)

docs: fix typos and similarly insignificant changes

Co-authored-by: zeertzjq <zeertzjq@outlook.com>
Co-authored-by: smjonas <jonas.strittmatter@gmx.de>
Co-authored-by: kanreki <32443233+kanreki@users.noreply.github.com>

src/nvim/api/command.c

@@ -650,7 +650,7 @@ static bool string_iswhite(String str)
       // Found a non-whitespace character
       return false;
     } else if (str.data[i] == NUL) {
-      // Terminate at first occurence of a NUL character
+      // Terminate at first occurrence of a NUL character
       break;
     }
   }