Log Message:
sheldon: update to 0.8.0. Changes:

### Breaking changes

- Remove deprecated config key and template filters

- Remove deprecated directory support

- Stop defaulting to Zsh and allow unspecified shell. This change stops
  the shell defaulting to Zsh when unspecified and allows you to use
  Sheldon without specifying a particular shell.

- Remove experimental Fish shell support. Sheldon is shell agnostic
  enough that you can still get support for Fish by overriding the
  default `match`, `apply`, and `templates` values in the config file.

### Features

- Support all clap complete shells. The `sheldon completions` command
  now supports all shells that clap supports, regardless of whether they
  are supported by Sheldon.

- Add Nix Flake support. This repository is now a flake, and can be
  installed using nix profile:

- Add feature flags to control dependency vendoring. This adds various
  Cargo features to control the vendoring of dependencies when
  installing Sheldon using Cargo. For example if you want to install
  Sheldon with a vendored OpenSSL you can use the following command.