[FR][UX] Dedicated config location possibility: `.docformatter.toml`

With some on-scale maintenance workflows, it's important to be able to put different tool configurations in their own config files. Like .flake8 or towncrier.toml.
One of such workflows is https://blog.jaraco.com/skeleton/, for example.

With the above in mind, I'd like to suggest adding support for a tool-specific config. It could be, for example, .docformatter.toml (I would be fine with just .docformatter and ini-parser but a lot of people prefer TOML these days).

I understand that it's possible to use --config with whatever filename I like but this would require passing it everywhere if the tool is to be used from different environments (like pre-commit and various editors). Doing so adds to the maintenance burden, while this FR's motivation is to reduce it.

Start by locating the existing --config entry point and configuration parsing behavior. Compare the proposed .docformatter.toml and .docformatter options, including how they would work from pre-commit and editors. Done should mean a documented tool-specific configuration location is discovered consistently without requiring --config.