The code of the third exercise answer of Implementing Game of Life is broken

[SomeoneToIgnore]

Describe the bug Last task of the section proposes to use fixedbitset crate, giving incomplete instructions on how to implement a task: the updated code for the constructor is missing. Even though it's simple to implement, it might be useful to add it into the answer also.

But even if the constructor code is updated, the code provided in the answer does not compile with the latest fixedbitset crate version because:

• the answer has the code line pub fn cells(&self) -> *const Cell { but the bitset crate returns &[u32] from its as_slice method: https://github.com/bluss/fixedbitset/blob/master/src/lib.rs#L200

• the answer has the code

  next.set(idx, match next_cell {
  Cell::Alive => true,
  Cell::Dead => false,
  });

  but does not say how to adjust the match statement. It should be done due to bitset returning bool when accessed by index: https://github.com/bluss/fixedbitset/blob/master/src/lib.rs#L477

To Reproduce Steps to reproduce the behavior:

1. Go to https://rustwasm.github.io/book/game-of-life/implementing.html#exercises
2. Open the third exercise answer
3. Apply it to the project (use fixedbitset = "0.1.9")
4. Compile the project
5. See compilation error

Expected behavior There are no compilation errors

Additional context

• Have also adjusted bitIsSet to compare the values with === instead of == to make it more safe. The change seems to be too tiny for a separate PR and issue.
• Display implementation for Universe is also affected by the bitset usage, but since it's not used at this stage of the tutorial, we might want to add a note that the implementation and render method should be removed as not used.
• We might want to explicitly specify the fixedbitset crate version to avoid confusion in the future