chore: generate shell completions on brew install

Signed-off-by: Nick Hale <[email protected]>

Author: njhale

.goreleaser.yml

@@ -59,6 +59,7 @@ release:
 brews:
   - description: "GPTScript CLI"
     install: |
+      generate_completions_from_executable(bin/"gptscript", "completion", shells: [:bash, :zsh, :fish])
       bin.install "gptscript"
     homepage: "https://github.com/gptscript-ai/gptscript"
     skip_upload: false