ci: dont run github_pages on forks

Limit to not automatically run on forks and allow ad-hoc runs.

Signed-off-by: Austin Horstman <khaneliman12@gmail.com>

.github/workflows/github_pages.yml

@@ -3,8 +3,10 @@ on:
   push:
     branches:
       - master
+  workflow_dispatch:
 jobs:
   publish:
+    if: github.event_name != 'schedule' || github.repository_owner == 'nix-community'
     strategy:
       matrix:
         os: [ubuntu-latest]