Move hello world example to second section (#1838)

The current location for the hello world example is awkward since the
two surrounding pages are both talking about Rust from a high level
without talking about syntax at all. I think starting the second section
(types and values) with the hello world example would help the first
section flow more smoothly.

src/types-and-values/hello-world.md

@@ -0,0 +1,48 @@
+---
+minutes: 5
+---
+
+# Hello, World
+
+Let us jump into the simplest possible Rust program, a classic Hello World
+program:
+
+```rust,editable
+fn main() {
+    println!("Hello 🌍!");
+}
+```
+
+What you see:
+
+- Functions are introduced with `fn`.
+- Blocks are delimited by curly braces like in C and C++.
+- The `main` function is the entry point of the program.
+- Rust has hygienic macros, `println!` is an example of this.
+- Rust strings are UTF-8 encoded and can contain any Unicode character.
+
+<details>
+
+This slide tries to make the students comfortable with Rust code. They will see
+a ton of it over the next four days so we start small with something familiar.
+
+Key points:
+
+- Rust is very much like other languages in the C/C++/Java tradition. It is
+  imperative and it doesn't try to reinvent things unless absolutely necessary.
+
+- Rust is modern with full support for things like Unicode.
+
+- Rust uses macros for situations where you want to have a variable number of
+  arguments (no function [overloading](../control-flow-basics/functions.md)).
+
+- Macros being 'hygienic' means they don't accidentally capture identifiers from
+  the scope they are used in. Rust macros are actually only
+  [partially hygienic](https://veykril.github.io/tlborm/decl-macros/minutiae/hygiene.html).
+
+- Rust is multi-paradigm. For example, it has powerful
+  [object-oriented programming features](https://doc.rust-lang.org/book/ch17-00-oop.html),
+  and, while it is not a functional language, it includes a range of
+  [functional concepts](https://doc.rust-lang.org/book/ch13-00-functional-features.html).
+
+</details>