* Re-implement completion system:
* Remove optional dependency `click-completion` (with its sub-dependencies, like Jinja).
* Add optional dependency `shellingham` to auto detect shell to install (it was used by `click-completion`).
* Completion now doesn't require a third party library.
* If `shellingham` is not installed/added as a dependency, `--install-completion` and `--show-completion` take a value with the name of the shell.
* Fix support for user provided completion in *CLI Parameters*.
* Fix completion for files in Bash, Zsh, and Fish.
* Add support for modern versions of PowerShell, 5, 6, and 7 (e.g. in Windows 10).
* Add support for `pwsh` (PowerShell Core).
* PowerShell support includes help strings for commands and *CLI Parameters*.
* Several bug fixes.
* Tests for the completion logic/code.
* Tested in all the shells in Linux and Windows.
* PR [66](https://github.com/tiangolo/typer/pull/66).
* Fix format in docs with highlighted lines. PR [65](https://github.com/tiangolo/typer/pull/65).
* Add docs about [Typer CLI - completion for small scripts](https://typer.tiangolo.com/typer-cli/). PR [#64](https://github.com/tiangolo/typer/pull/64).
* Add docs about [Alternatives, Inspiration and Comparisons](https://typer.tiangolo.com/alternatives/). PR [#62](https://github.com/tiangolo/typer/pull/62).
* Add [Development - Contributing Guide](https://typer.tiangolo.com/contributing/). PR [#61](https://github.com/tiangolo/typer/pull/61).