zsh,nix: source nix.sh from user's nix-profile

add 'chisui/zsh-nix-shell' and 'spwhitt/nix-zsh-completions' plugins
with sheldon

.config/sheldon/plugins.toml

@@ -17,5 +17,11 @@ github = 'djui/alias-tips'
 [plugins.fast-syntax-highlighting]
 github = 'zdharma-continuum/fast-syntax-highlighting'
 
+[plugins.zsh-nix-shell]
+github = 'chisui/zsh-nix-shell'
+
+[plugins.nix-zsh-completions]
+github = 'spwhitt/nix-zsh-completions'
+
 [plugins.zsh-vi-mode]
 github = 'jeffreytse/zsh-vi-mode'

.zshrc

@@ -197,3 +197,5 @@
  }
 
  eval "$(starship init zsh)"
+
+ if [ -e ~/.nix-profile/etc/profile.d/nix.sh ]; then . ~/.nix-profile/etc/profile.d/nix.sh; fi # added by Nix installer...and kept by me