Turn exercices 013 to 022 into practice

[cuihtlauac]

This task consists of doing 10 exercises instead of one, as described in issues #2167, #2168, #2170, #2172, #2173, #2176, #2177, #2178, #2179 and #2180. Create 10 folders (from 013 to 022), and populate them as the others. Makes sure dune build --root . and dune test --root . answer work.

• 013 Turned exercise 013 into practice #2204
• 014 Turned exercise 014 into practice #2206
• 015 Turned exercise 015 into Practice. #2207
• 016 Turned exercise 016 into Practice. #2208
• 017 Turned exercise 017 into practice. #2209
• 018 Turned exercise 018 into practice #2210
• 019 Turned exercise 019 into practice #2213
• 020 Turned exercise 020 into practice #2214
• 021 Turned exercise 021 into practice #2215
• 022 Turned exercise 022 into practice #2216

[divyankachaudhari]

I'd like to work on this. Thank you.

[cuihtlauac]

Yes @divyankachaudhari, you may work on this one. Please do not use git push forcefully in your PR, adding commits is easier.

[divyankachaudhari]

@cuihtlauac noted 🫡 I have a question, I'll create separate commits but do I include all the exercises in one PR itself?

[cuihtlauac]

Let's create separate PRs it will be easier to review

[cuihtlauac]

All PR merged, closing