add alt text to Repos Python badge

[MichaelCurrin]

[![Go to Python website](https://img.shields.io/badge/dynamic/toml?url=https%3A%2F%2Fraw.githubusercontent.com%2FMichaelCurrin%2Fimage-to-pdf-py%2Frefs%2Fheads%2Fmain%2Fpyproject.toml&query=project.requires-python&label=python&logo=python&logoColor=white)](https://python.org)

"Go to Python website"

Tried to set this already but it is lost