[Hello World]: Added comment to stub and Instruction Append

[BethanyG]

Please see this forum discussion for details.

Added a comment to warn students that they need to adjust the export line in the stub file:

  (func (export "hello") (result i32 i32)
    (i32.const 64) (i32.const 14)
  )

"Goodby, Mars!" is 14, but "Hello, World!" is 13, so if (i32.const 14) is not changed, the student won't pass the tests.

Also added a caution level instruction append to alert students.

Conversely, the stub can be altered so that it is already 13 -- but then it won't match "Goodby, Mars!".

[iHiD]

Thank you! 💙

@ErikSchierboom You happy with this - if so, let's merge it before Nov starts pls! :)

[bushidocodes]

LGTM. A tiny nit is that "Web Assembly" should be written as one word "WebAssembly." I've approved because it's not worth delaying this given how close we are to the start of the month.

[BethanyG]

@bushidocodes -- corrected. Thanks for pointing it out! 😄

[BethanyG]

@ErikSchierboom @bushidocodes - ready for merge (I think!).

[ErikSchierboom]

Thanks!