Adds new integration [thastealth/alfen_modbus]

[ThaStealth]

Checklist

• I've read the publishing documentation.
• I've added the HACS action to my repository.
• (For integrations only) I've added the hassfest action to my repository.
• The actions are passing without any disabled checks in my repository.
• I've added a link to the action run on my repository below in the links section.
• I've created a new release of the repository after the validation actions were run successfully.

Links

Link to current release: https://github.com/ThaStealth/alfen_modbus/releases/tag/v0.1.0
Link to successful HACS action (without the ignore key): https://github.com/ThaStealth/alfen_modbus/actions/runs/5967909530/job/16190586420
Link to successful hassfest action (if integration): https://github.com/ThaStealth/alfen_modbus/actions/runs/5967909530/job/16190586646

[hacs-bot]

The submitted name thastealth/alfen_modbus does not match what GitHub returns for the repository (ThaStealth/alfen_modbus).

[frenck]

The bot commented about an issue with this PR a few months ago; as this still hasn't been addressed, I'll consider this PR to be stale and will, therefore, close it up.

Feel free to re-open this PR when you are ready to work on it again.

../Frenck