Devcontainer-manager

Added
- added message with template path after running generate with global template

Added
- added flag `--build` to `generate` subcommand that runs docker build after
config generation
- added `--version` flag

Fixed
- fixed crash for python < 3.9 due to wrong type annotations
- added missing required packages `pydantic` and `pydantic_yaml`

Added
- added config key `base_config` that accepts list of other configs, these configs
will be merged in list order

Changed
- completely rewriten configs to pydantic
- global config structure was changed, to migrate, change:
- `global_defaults` renamed to `defaults`
- `aliases` moved to separate config - `aliases.yaml`
- added new option `override_config_path` by default `overrides.yaml`
- config structure migration:
- rename `additional_options_json` to `additional_options`
- changed `devcontainer_manager generate` arguments - now it accepts multiple configurations
which will be merged in order of arguments from left to right

Changed
- switched PyYAML to ruamel.yaml - yaml comments in configs will now be preserved

Fixed
- fixed config list items being deduplicated and shuffled

Changed
- disabled default flow style dumping for older yaml versions

Fixed
- included missing default configs in package