Snakefile: add GITHUB_PR and others to metadata (#131)

Snakefile

@@ -132,6 +132,9 @@ cat > {output} <<EOF
   "CI_PIPELINE_ID": "${{CI_PIPELINE_ID:-}}",
   "CI_PIPELINE_SOURCE": "${{CI_PIPELINE_SOURCE:-}}",
   "CI_PROJECT_ID": "${{CI_PROJECT_ID:-}}",
+  "GITHUB_REPOSITORY": "${{GITHUB_REPOSITORY:-}}",
+  "GITHUB_SHA": "${{GITHUB_SHA:-}}",
+  "GITHUB_PR": "${{GITHUB_PR:-}}",
   "PIPELINE_NAME": "${{PIPELINE_NAME:-}}"
 }}
 EOF