refactor: ✏️ use update, not add for Quarto extension (#195)

# Description

This PR needs a quick review.

## Checklist

- [x] Ran `just run-all`

---------

Co-authored-by: Signe Kirk Brødbæk <40836345+signekb@users.noreply.github.com>

Author: lwjohnst86

justfile

@@ -20,7 +20,8 @@ install-precommit:
 
 # Update the Quarto seedcase-theme extension
 update-quarto-theme:
-  quarto add seedcase-project/seedcase-theme --no-prompt
+  # Add theme if it doesn't exist, update if it does
+  quarto update seedcase-project/seedcase-theme --no-prompt
 
 # Update files in the template from the copier parent folder
 update-template:

template/justfile.jinja

@@ -33,7 +33,8 @@ install-precommit:
 {%- if is_seedcase_project %}
 # Update the Quarto seedcase-theme extension
 update-quarto-theme:
-  quarto add seedcase-project/seedcase-theme --no-prompt
+  # Add theme if it doesn't exist, update if it does
+  quarto update seedcase-project/seedcase-theme --no-prompt
 {%- endif %}
 
 # Install Python package dependencies