docs: rework completions section (#5879)

Co-authored-by: Bjorn Neergaard <bjorn@neersighted.com>

docs/_index.md

@@ -282,42 +282,60 @@ To uninstall Poetry, simply delete the entire `$VENV_PATH` directory.
 `poetry` supports generating completion scripts for Bash, Fish, and Zsh.
 See `poetry help completions` for full details, but the gist is as simple as using one of the following:
 
+### Bash
+
+#### Auto-loaded (recommended)
 
 ```bash
-# Bash
-poetry completions bash > /etc/bash_completion.d/poetry
+poetry completions bash >> ~/.bash_completion
+```
 
-# Fish
-poetry completions fish > ~/.config/fish/completions/poetry.fish
+#### Lazy-loaded
 
-# Zsh
-poetry completions zsh > ~/.zfunc/_poetry
-
-# Oh-My-Zsh
-mkdir $ZSH_CUSTOM/plugins/poetry
-poetry completions zsh > $ZSH_CUSTOM/plugins/poetry/_poetry
+```bash
+poetry completions bash > ${XDG_DATA_HOME:~/.local/share}/bash_completion/completions/poetry
+```
 
-# prezto
-poetry completions zsh > ~/.zprezto/modules/completion/external/src/_poetry
+### Fish
 
+```fish
+poetry completions fish > ~/.config/fish/completions/poetry.fish
 ```
 
-{{% note %}}
-You may need to restart your shell in order for the changes to take effect.
-{{% /note %}}
+### Zsh
 
-For `zsh`, you must then add the following lines in your `~/.zshrc`
+```zsh
+poetry completions zsh > ~/.zfunc/_poetry
+```
+
+You must then add the following lines in your `~/.zshrc`, if they do not already exist:
 
 ```bash
 fpath+=~/.zfunc
 autoload -Uz compinit && compinit
 ```
 
-For `oh-my-zsh`, you must then enable poetry in your `~/.zshrc` plugins
+#### Oh My Zsh
+
+```zsh
+mkdir $ZSH_CUSTOM/plugins/poetry
+poetry completions zsh > $ZSH_CUSTOM/plugins/poetry/_poetry
+```
+You must then add `poetry` to your plugins array in `~/.zshrc`:
 
 ```text
 plugins(
  poetry
  ...
  )
 ```
+
+#### prezto
+
+```zsh
+poetry completions zsh > ~/.zprezto/modules/completion/external/src/_poetry
+```
+
+{{% note %}}
+You may need to restart your shell in order for these changes to take effect.
+{{% /note %}}