Vscode-task-runner

Handle unknown shells in the same manner as VS Code, by adding `-c` before the command.

Fixes 45

- Add support for `${input:id}` variables
- Values can be provided interactively or through `VTR_INPUT_id` environment variables
- Better shell defaults on Windows
- All exceptions raised (besides things like `KeyError`s) are now custom exception types and not generic `ValueError`s

Breaking changes:
- Exception will now be raised when an unsupported variable is encountered, rather than skipped over
- Variables will only be replaced under `command`, `args`, and `options` keys per VS Code docs: https://code.visualstudio.com/docs/editor/tasks#_variable-substitution:~:text=Note%3A%20Not%20all%20properties%20will%20accept%20variable%20substitution.%20Specifically%2C%20only%20command%2C%20args%2C%20and%20options%20support%20variable%20substitution.

Add support for new predefined variables in VSCode 1.86

Dependency updates.

Set minimum `shellingham` version to fix MacOS bug

Make it easier to add extra arguments