Remove exotic string types from scalar type slide (#593)

When teaching the class, I’ve noticed that raw strings and byte
strings tend to cause confusion. The slide is meant to be a friendly
introduction and show how Rust is similar to other languages like C
and C++. Instead, the string types cause a ton of questions which are
unnecessary at this early point.

The information is still there, but now in the form of a speaker note.

src/basic-syntax/scalar-types.md

@@ -5,9 +5,8 @@
 | Signed integers        | `i8`, `i16`, `i32`, `i64`, `i128`, `isize` | `-10`, `0`, `1_000`, `123i64` |
 | Unsigned integers      | `u8`, `u16`, `u32`, `u64`, `u128`, `usize` | `0`, `123`, `10u16`           |
 | Floating point numbers | `f32`, `f64`                               | `3.14`, `-10.0e20`, `2f32`    |
-| Strings                | `&str`                                     | `"foo"`, `r#"\\"#`            |
+| Strings                | `&str`                                     | `"foo"`, `"two\nlines"`       |
 | Unicode scalar values  | `char`                                     | `'a'`, `'α'`, `'∞'`           |
-| Byte strings           | `&[u8]`                                    | `b"abc"`, `br#" " "#`         |
 | Booleans               | `bool`                                     | `true`, `false`               |
 
 The types have widths as follows:
@@ -16,3 +15,29 @@ The types have widths as follows:
 * `isize` and `usize` are the width of a pointer,
 * `char` is 32 bit wide,
 * `bool` is 8 bit wide.
+
+<details>
+
+There are a few syntaxes which are not shown above:
+
+- Raw strings allow you to create a `&str` value with escapes disabled: `r"\n"
+  == "\\\\n"`. You can embed double-quotes by using an equal amount of `#` on
+  either side of the quotes:
+
+  ```rust,editable
+  fn main() {
+      println!(r#"<a href="link.html">link</a>"#);
+      println!("<a href=\"link.html\">link</a>");
+  }
+  ```
+
+- Byte strings allow you to create a `&[u8]` value directly:
+
+  ```rust,editable
+  fn main() {
+      println!("{:?}", b"abc");
+      println!("{:?}", &[97, 98, 99]);
+  }
+  ```
+
+</details>