Configue

Breaking changes
- Remove support for Python < 3.8

Features
- `()` can now load object attributes, such as static methods (e.g. `(): module.MyClass.generate`)

Features
- `!ext` can now load object attributes, such as enum members (e.g. `!ext module.MyEnum.MY_VALUE`)

Fixes
- Fixed loading `!import` or `!cfg` tags in a `!cfg` tag

Features
- Added a `logging_config_path` keyword parameter to `configue.load` to set up a logging configuration while loading a
configuration file

Fixes
- Loading a null `!path` will now return `None` instead of raising an Exception

Breaking changes
- The `!env` tag has been removed, environment variables can now be loaded anywhere
- The `cfg://` syntax has been replaced with `!cfg path.to.value`
- `!cfg` now redirects to a path in the current file (instead of the first loaded file)
- Use `!import` to load a path in another file
- The `ext://module.submodule.object` syntax has been replaced with `!ext module.submodule.object`
- Replaced `load_config_from_file` with a `configue.load` function, which is now the main entrypoint of the library
- use `configue.load("/path/to/file.yml")` to load a file
- use `configue.load("/path/to/file.yml", "path.to.section")` to load only a section of a file
- loading a path in a file recursively loads all children (replaced the lazy-loading with path loading),
see README for more details
- Removed the `load_config_from_dict` function
- The `!list` tag has been removed, set your environment variable to `[value_1, value_2]` instead

Migration guide
- Remove all `!env` tags
- Remove all `!list` tags, and replace your environment variables from `value1,value2` to `[value1,value2]`
- Replace `ext://path.to.load` with `!ext path.to.load`
- If you are using `!import` to import a file containing values with `cfg://path.to.load`, replace the `cfg://...` with
`!import:path/to/root/file.yml path.to.load`
- Replace `cfg://path.to.load` with `!cfg path.to.load`
- Replace `configue.load_config_from_file(...)` with `configue.load(...)`
- Replace `configue.load_config_from_file(...)["path"]["to"]["load"]` with `configue.load(..., "path.to.load")`

Features
- The `!import` tag can now specify the path to load in the other file, with the syntax:
`!import:path.to.load path/to/file.yml`
- Dictionaries and lists are now JSON dumpable and picklable

Fixes
- Removed warning about missing environment variables from unloaded paths