Add exercise: two-fer

[simisc]

Add the Two-Fer practice exercise.

[github-actions]

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[vaeng]

I just looked over the general structure and a bit of the Fortran code. I cannot comment too much on the code, as my Fortran is not very good. It looks fine on the "exercism meta" structure side.

Thanks for taking the job and adding more exercises :)

[ErikSchierboom]

@simisc Thanks! I've added @pclausen as a reviewer

[iHiD]

Just to weigh in:

• This passes the CI [1]
• The "quality" of the example file doesn't really matter as it's a practice exercise
• The tests look really clean

So let's give @pclausen a day or two to reply, but I'm in favour of taking a relatively optimistic merging approach to this if he doesn't get round to it! :)

Thanks @simisc!

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[1]

[ErikSchierboom]

Absolutely. But I did want to give @pclausen the chance to review :)

[simisc]

I've reduced indentation from 3 to 2 spaces for consistency with the other exercises in the track. The online Fortran editor also uses 2 spaces, so the stub file should start with the same formatting.

[ErikSchierboom]

Thanks!