Add Elixir-specific note to Hamming instructions

[tolbier]

Summary

• Adds an instructions.append.md for the Hamming exercise clarifying that it's intended to reinforce Enum usage, while noting it can also be solved with other methods.

Motivation

While solving this exercise, I started with an Enum-based approach and later rewrote it using recursion/pattern matching, realizing the exercise's intent (practicing Enum) wasn't explicit anywhere in the instructions.

Test plan

• N/A (docs-only change)

[github-actions]

Thank you for contributing to exercism/elixir 💜 🎉. This is an automated PR comment 🤖 for the maintainers of this repository that helps with the PR review process. You can safely ignore it and wait for a maintainer to review your changes.

Based on the files changed in this PR, it would be good to pay attention to the following details when reviewing the PR:

• General steps

  • 🏆 Does this PR need to receive a label with a reputation modifier (x:size/{tiny,small,medium,large,massive})? (A medium reputation amount is awarded by default, see docs)

• Any exercise changed

  • 👤 Does the author of the PR need to be added as an author or contributor in <exercise>/.meta/config.json (see docs)?
  • 🔬 Do the analyzer and the analyzer comments exist for this exercise? Do they need to be changed?
  • 📜 Does the design file (<exercise>/.meta/design.md) need to be updated to document new implementation decisions?

• Practice exercise changed

  • 🌲 Do prerequisites, practices, and difficulty in config.json need to be updated?
  • 🧑‍🏫 Are the changes in accordance with the community-wide problem specifiations?

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Automated comment created by PR Commenter 🤖.

[angelikatyborska]

Hi! What makes you believe that Hamming must be solved using the Enum module?

[IsaacG]

@tolbier Are you still working on this?

[angelikatyborska]

I'm closing this PR due to the lack of contact from the author. Seeing how the commit was authored with Claude, I am assuming the human PR author might not even be aware that this PR got submitted.