Support custom swing_mode for climate

**Describe the problem you have/What new integration you would like**
swing_mode does not match at all with what my ACs support.

**Please describe your use case for this integration and alternatives you've tried:**
I'm currently adding https://github.com/DomiStyle/esphome-panasonic-ac to control my Panasonic ACs, I'm doing some changes of my own as well, it happens that swing_mode does not support at all what my ACs support, I can set them to point up, up middle, middle, down middle, down, or swing this applies only to vertical, one of the ACs supports horizontal in the same fashion, left, left mid etc.

In order to avoid breaking current integrations I think the simplest approach would be to add custom_swing_mode just like what's already supported for presets or fan modes

**Additional context**

No project files, tests, or entry points are named. Start by reviewing the esphome-panasonic-ac integration and the existing custom preset or fan-mode support referenced in the request; done means the compatible API design and supported vertical and horizontal swing values are agreed.

Written by the indexing model from the issue text.