Fix invalid link to the counting section

src/macros-practical.md

@@ -655,7 +655,7 @@ fn main() {
 Let's tackle a harder one: how to turn `inits` into both the array literal `[0, 1]` *and* the array
 type, `[$sty; 2]`. The first one we can do like so:
 
-```ignore
+```rust,ignore
  Recurrence { mem: [$($inits),+], pos: 0 }
 // ^~~~~~~~~~~ changed
 ```
@@ -803,7 +803,7 @@ macro_rules! count_exprs {
 ```
 
 > **<abbr title="Just for this example">JFTE</abbr>**: this is not the *only*, or even the *best*
- way of counting things. You may wish to peruse the [Counting](.blocks/counting.html) section
+ way of counting things. You may wish to peruse the [Counting](./blocks/counting.html) section
  later.
 
 With this, we can now modify `recurrence` to determine the necessary size of `mem`.

src/macros/minutiae/debugging.md

@@ -128,6 +128,9 @@ But not just `rustc` exposes means to aid in debugging macros. For the aforement
 [`cargo-expand`](https://github.com/dtolnay/cargo-expand) made by [`dtolnay`](https://github.com/dtolnay)
 which is basically just a wrapper around it.
 
+You can also use the [playground](https://play.rust-lang.org/), clicking on its `TOOLS` button in
+the top right gives you the option to expand macros right there!
+
 Another amazing tool is [`lukaslueg`'s](https://github.com/lukaslueg)
 [`macro_railroad`](https://github.com/lukaslueg/macro_railroad), a tool that allows you visualize
 and generate syntax diagrams for Rust's `macro-by-example` style macros. It visualizes the accepted